MAKING THE
SMALL SHOP PROFITABLE
Making the Small Shop Profitable
Making
The Small Shop Profitable
By
John H. Van Deventer, M.E., Memb.A.S.M.E.
EDITOR-IN-CHIEF THE AMERICAN MACHINIST
AUTHOR, "SUCCESS IN THE SMALL SHOP," "HANDBOOK OF MACHINE
SHOP MANAGEMENT," CO-AUTHOR, ''MANUFACTURE
OF ARTILLERY AMMUNITION"
FIRST EDITION
PUBLISHED BY THE AMERICAN MACHINIST
McGRAW-HILL BOOK COMPANY, INC.
SOLE SELLING AGENTS
239 WEST 39TH STREET, NEW YORK
1918
COPYRIGHT, 1918, BY THE McGRAW-HILL BOOK COMPANY, INC.
w d
FOREWORD
For years the word " Small Shop " conveyed to one's mind the impression of hard work and no profits. The owner of a small shop was regarded with pity and looked upon as one having the responsibilities of a capitalist and the net income of a day laborer. Small shop ownership was a temporary affair and the sign painter made frequent visits to the same institution to change the -name of the proprietor on the " shop shingle."
Now the small shop is recognized as an honorable and also a profitable institution.
The change itself and the recognition of the position of the small shop by the mechanical public has been materially helped and in fact largely effected by the American Machinist's " Small Shop Series " which was the first consistent attempt to help the small shop find itself and to help the mechanical public to find the small shop.
So effective was this series that after publication in the American Machinist, re- peated demand made necessary the republication of these articles in book form. The first fifty articles were gathered together under the title of " Success in the Small Shop," of which successive editions have been printed in response to the demand of those interested in making small shops successful.
The present volume " Making the Small Shop Profitable " is a collection of the later writings of the same author on important phases of small shop activity. It contains also an illustrated encyclopedia of small shop methods or " kinks " which should prove of the utmost practical value to the mechanic whose means for doing work are restricted to what is ordinarily found in the small shop.
THE AUTHOR.
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CONTENTS
PAGE
PREFACE v
GETTING " INTO " THE SMALL SHOP 1
LIMITING IMPROVEMENTS IN THE SMALL SHOP 3
USING SKILL FOB CAPITAL IN THE SMALL SHOP 5
FINDING THE TURNING POINT IN THE SMALL SHOP 7
WEIGHING PATTERNS AND CASTINGS BY DISPLACEMENT OF WATER 9
SPRING FEVER IN THE SMALL SHOP '. 10
MAKING PATTERNS AND CASTINGS FOR THE SMALL SHOP 12
THE SMALL SHOP GRINDING WHEEL 14
THE SMALL SHOP GRINDER 17
A HANDY CLIP FOR HANGING WET BLUEPRINTS 19
KNURLING IN THE SMALL SHOP 20
SCREW THREADS IN THE SMALL SHOP 25
MEASURING SCREW THREADS IN THE SMALL SHOP 28
LIFTING THE SHAPEB CHUCK 30
HARDENING AND SOFTENING STEEL IN THE SMALL SHOP 31
BORING PUMP CHAMBERS IN THE DRILLING MACHINE 33
A HANDY DRIVER FOR KEMOVING SHELL SOCKETS 33
CARBONIZING SMALL SHOP STEELS 34
CASEHARDINO SMALL SHOP STEELS 36
TAKING SMALL SHOP TEMPERATURE 38
PAINTING SMALL SHOP PRODUCTS 41
CARING FOR SMALL SHOP BEARINGS 47
A BUILT UP LIMIT GAGE 49
SPECIAL FORM OF HOLLOW MILL . 49
RADIUS PLANING TOOLS 49
METHODS OF LOCATING MACHINERY FOUNDATION 50
END MILL FOR BABBITT 52
STANDARDISING SHOP DRAWINGS FOR MACHINE DETAILS 53
LUBRICATING OILS AND CUTTING COMPOUNDS FOR SHOP USE 56
PREVENTING LORAL SHRINKAGE IN ALUMINUM CASTING 61
ADJUSTABLE DRIVE 61
WENCH, VISE AND ASSEMBLING METHODS 62
DEVICES THAT MAKE LATHES PROFITABLE 63
MONEY SAVING ASSEMBLING METHODS 64
PROFIT MAKING DEVICES FOR TURNING 65
BORING AND TURNING KINKS 66
A VARIETY OF TIME SAVING KINKS 67
CONTENTS
PAGE
A NUMBER OF IDEAS FOR PLANERS 68
GRIPPING AND HANDLING KINKS 69
CHUCKS AND TUBNING 70
HANDY KINKS FOR THE HANDY MAN 71
HELPING THE DRILLING MACHINE TO EAKN A PROFIT 72
VARIOUS LOCKNUT AND LOCKING DEVICES 74
Six HELPS FOR THE SMALL SHOP LATHE 78
CONVENIENT KINKS FOR THE SMALL SHOP ASSEMBLES 79
SOME USEFUL PLANER KINKS 80
A VARIETY OF EXPANDING ARBORS 81
IDEAS FOR THE SMALL SHOP BLACKSMITH 82
PLANER AND SHAPEH DEVICES THAT SAVE MONEY 84
A COLLECTION OF BELT CUTTING DEVICES 85
A NUMBER OF WAYS TO CUT PINS IN QUANTITIES 86
SPRING WINDING AND CUTTING 87
VARIOUS METHODS OF DRIVING AND PULLING BUSHINGS 88
MAKING THE DRILLING MACHINE EARN DIVIDENDS 90
BENCH AND VISE KINKS OF SHOP VALUE 91
STUNTS THAT MAKE SHAPEHS EARN PROFITS AND PAY DIVIDENDS . 92
A COLLECTION OF BENCH AND VISE KINKS 93
SLIDE REST KINKS AND CUTTING TOOL STUNTS . 94
HINTS THAT WILL HELP THE EFFICIENT LATHE HAND .95
GEAR DENTISTRY AND OTHER KINKS 96
SEVEN APPLICATIONS OF " OLD MEN " 97
VARIOUS WAYS OF PULLING KEYS . 99
WORK BENCH AND OTHER KINKS . 100
MORE VISE KINKS 102
KNEE AND FOOT OPERATING DEVICES FOR THE BENCH 103
CLAMPING AND HOLDING MATERIAL IN VISES 104
USEFUL DEVICES FOR THE SHOP 105
HAND WHEEL SPANNERS AND OTHER KINKS . 106
VARIOUS TYPES OF JACKS AND CLAMPS 107
INTERNAL, EXTERNAL AND END LAPPING DEVICES . . . .108
ROUGH INTERNAL LAPPING DEVICES 109
DIFFERENT TYPES OF PIPE HANGERS '...'.. 110
INDEX . . Ill
Getting "Into" the Small Shpp
BY JOHN H. VAN DEVENTEE
SYNOPSIS — Some customers have developed highly efficient ways of working up a fictitious credit, with the object of "putting one over " on the small shop when the time is ripe. This article re- lates one such instance, which had the effect of closing the doors of a small marine repair shop. Incidentally it introduces the reader to Dave Hope, the Knight-Errant Machinist.
" Kivet a washer on the end of your cold chisel, Sonny ! "
Dave Hope addressed this bit of advice to the new ap- prentice, whose hand was swollen to twice its natural size as the result of well-intentioned but misaimed hammer blows. The lad has passed the stage of looking for left- hand monkey-wrenches and of being sent from machine to machine in search for the key of the big planer, and was now learning the rudiments of chipping. Dave Hope's repair -shop was a good place in which to learn this art, for there were plenty of castings to chip, and hardly any two of them were alike. Incidentally it was a great privilege for a boy to learn his trade in Dave's shop, for its owner was a real " all around " machinist, and an apprentice trained by him was able to use both head and hands when he stepped out of his time.
It will not be amiss to introduce Dave to you with a description of the man and a brief outline of his check- ered career, for it is my hope to be able to recount from time to time during the year some of the most interest- ing of his adventures in small shops. Please overlook the single grimy finger that he extends you in greeting, and grasp him by the hand, for I know that American* Machinist readers', will not hesitate because of the signs of honest toil that are upon it.
Dave is one of those men whose age it is hard to tell from his appearance. The youthful expression of his face seems to contradict the evidence presented by his white hair and mustache, and his tall, somewhat spare figure is as -active as that of a man of 30. He started to serve his time in a railroad repair shop when a boy of 12, in the days 'when a railroad-shop apprenticeship meant a much more varied experience than it does at present. A few years of knocking about the country followed this, during which he carefully avoided the big "manufac- turing shops," for Dave, as he says himself, " never did have a; liking for doing the same thing twice."
DAVE HOPE, THE KNIGHT-ERRANT MACHINIST
One fairly large repair shop in the West Virginia coal fields held him for 18 months — not because Dave was be- ginning to settle down, but because he had a good paying job as foreman, and board was cheap. He was beginning to get the " shop of his own " idea, and this seemed like a. good chance to get the necessary money to start with. It was while here that Dave Hope's hair turned gray, due to being caught by a " fall " while directing the instal- lation of a receiver on an air line in the lower level. Three days in darkness after the safety lamps burned out left their physical effect upon him, but seemed to make no impression on his, spirit; or if any, it was to strengthen his disregard of danger or obstacles standing in the way.
Then began his adventur'-j^ ;y?itl>' email', shop's of his own — many of them, but one shop at a time — most of them disastrous financially, for Dave is no " captain of industry," but rather a " knight-errant machinist " who loves to venture where those seeking more substantial re- turn fear to tread. And while he has attended the ob- sequies of more defunct plants than any other man of my acquaintance, the funeral services are scarcely over be- fore you find Dave installed in another shop in which he does what he pleases in the way that suits him best. While these many changes have kept him rather poor in pocket, they have made him rich in experience and char- acter, and as a curious result he has a sort of camp fol- lowing among those who work for him. Thus as I leaned against the bench and heard him deliver the fore- going words of. advice to the apprentice, I could pick out among those working about the shop, faces which I had seen both in his shop in Philadelphia and in the one in Kansas City, where our acquaintance began.
THE KIND OF EXPERIENCE THAT STICKS ^ :•
" That kid with the sore thumb is getting experience," remarked Dave. "We all get it that way, and it's the only way that seems to stick. Life is a series of bumps from the time you slide off the first step till you hit the bottom landing. It's all in getting used to it. You can even get so you like it, as the boy did who had the measles three times. Sometimes it's a money loss, sometimes a machine won't work as you expect, and sometimes a dis- appointment in human nature. The hardest kind of a bump is when a man you trust goes back on you. I've had a number of such experiences, and while I can look back now and see the funny side of them, the sore spot lasted much longer than it did with the ordinary kind of bumps.
" Maybe it will interest your readers to hear of a lesson I learned about extending credit. I hope other small- shop owners may profit by it, and that it will help some of them to avoid paying the price that I did for this kind of experience.
" If you've been along Long Island Sound during the summer season, you've noticed what a slew of motor boats and steam yachts there are dotting the bays outside of the summer-resort towns. I noticed this about nine years ago, and also that about five boat owners out of seven seemed to have trouble with their motors when they got 50 ft. away from the dock. Of course this wasn't to be wondered at. Many of the owners were clerks from the city who knew as much about taking care of an engine as that green apprentice boy does about swinging a hammer. The boats were mostly hand-me- downs; not merely second hand, but seventh or eighth hand, and in addition the gasoline that those alongshore dealers worked off on that bunch of innocents was so weak that it could hardly run even when the can was turned upside down.
" I didn't have a shop just at that time, and the idea struck me that here was an opportunity that a good me- chanic might turn to advantage. This was before the automobile became common, remember, and there were not many machinists in those days who understood the
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MAKING SMALL SHOPS PROFITABLE
kinks and troubles of small gasoline motors. At kv.st those that-I .fpimd in the existing shops along the water- front didn't 'know much about them, judging by the work they turned £«£..
" AfteK look ing' ;ii>6n| fcr a wesk or so, I ran across a place that looked good to me. The shop stood up on posts at the water's edge and had a dock of its own. The equipment was nothing to brag about, consisting of two lathes in fair condition, one of 16-iii. and one of 18-in. swing, a more or less dilapidated gap lathe built up to swing 48 in., a shaper that had seen better days, a pipe threader and two upright drills. I guess what really at- tracted me to the place more than anything else was seeing a small boy catch three fine flounders in quick succession from the end of the dock. It looked to me like a good place for a fisherman to locate!
" It was about the middle of June that I came into possession. I managed to get enough cash together to make a satisfactory first payment and started in to get some of the money back. Reddy Burke, that you see over there on the miller, was with me, and so was Sandy McPherson, the fellow with his back turned to us, who is fitting a key at that bench. People were just getting their boats out and a quite a bit of overhauling was to be done. A good many of them came to us because they knew we couldn't do any worse by them than the other shops and might possibly do better.
" At first most of the work was on small motors, one and two cylinders, ranging from 4 to 20 hp. We turned out good work on these, and the reputation brought us some of the larger boats and a better grade of work along with it. There was one boat that we couldn't touch. It was the largest craft that anchored at the port, a 90-ft. steam yacht with twin triple engines. It seems that in this world what you can't get is what you want most, and it bothered us a lot to see the work on that boat go to a fellow a quarter mile up the bay, especially as we knew what sort of mechanic he was. The ' Alice,' that was her name, made regular trips across the sound and carried passengers back and forth from the shore re- sorts on each side.
ALICE, WHERE ART THOU?
" Business kent un pretty good, and by the end of July we had taken in enough over and above expenses to make the second payment on the shop. At this rate we would be clear before the end of the season. Any reasonable man ought to have been satisfied with that, but in spite of it our fingers itched to get hold of the ' Alice ' and get a chance at work that was really worth while.
" One afternoon about four, we were all busy in the shop when somebody hailed from the end of the dock. I started out to find what was wanted and saw a short stout fellow climbing out of a dinghy that was tied to one of the spiles at the landing platform. When I got a look at his face I saw that he was Captain Skinner of the ' Alice.'
" ' Anybody here that understands high-pressure feed pumps ? ' he asked.
'' It took me about two minutes to explain to the cap- tain that there were three men in our shop who knew more about high-pressure feed pumps than any six that he could find if he offered a reward for them anywhere in the United States. I don't know whether he believed
it or not,' but ho was up against it, £o Sandy went out in the dinghy, taking his tool kit with him.
"He turned up again in an hour and a half with some' samples of mush that had clogged up the discharge check valve and prevented the pump from doing its work. ' Nothing the matter with the pumps,' said Sandy. ' The trouble was with the last butcher that overhauled it and put in cold-water packing! '
" Captain Skinner came to us to have his work done after that, and while all the jobs were small ones, it made us feel pretty good to think that the ' Alice ' had had to come to Hope's Marine Repair Shop at last. Nobody could have been any better pay than the captain; he never questioned a bill and settled each one within ten days,
" After the middle of August, work slacked up a bit. Most of the boats would be put up after Labor Day, and the owners were beginning to cut down expenses and get along with motors that would run at all, just as nowa- days you see a fine lot of decrepit auto tires displayed in the fall. We hadn't figured on this, and it hurt us more than I cared to admit.
A JOB THAT LOOKED LIKE A LIFE-SAVER
" It looked like a life-saver when, the day after Labor Day, Captain Skinner turned up with a three-weeks' job for us on the ' Alice ' — nothing less than a complete overhauling of the twin triple engines and all of the auxiliaries. The three of us moved over to the ' Alice ' next day with our tool kits, and settled down to three weeks of the hardest work we ever did. All of us had corns on our backs from working in the engine pit.
" At the start of the third week Captain Skinner asked me to try to finish up by the coming Saturday morning. As there was some work waiting for us at the shop, we decided to work overtime nights so as to be sure to clean up by Friday night. By Thursday noon we saw that we would finish within the limit, but we were all three so ' tired out and short-tempered that we had to invent new cuss words to pay our respects to each other, having exhausted all of the ordinary ones.
" Friday night we turned her over to the captain, everything shipshape and better than new. I figured that there was close to a thousand dollars' worth of time and material on that job, and it was worth every penny of it. The captain wanted to give her a trial spin Saturday morning and insisted that I go along with him to see that everything was all right; but in view of all of the work waiting at the shop this was impossible, so I told him to try her out with his own crew. I was sure of the job and knew it would be all right. I handed him the bill for the work, and he said he would settle next evening if nothing went wrong.
" We went to work at 6 o'clock next morning to catch up with the accumulated work. At 8 o'clock one of the boys looked out of the window and said that st3am was up on the ' Alice.' At 8 :30 she began to move, and we all rushed to the window to give her a wave for good luck. On she went down the bay toward the outlet, looking as pretty as a picture and making a good two knots more than she had been ca- pable of before we overhauled her. She rounded the headland, and we went back to work feeling that we had done a good job.
" We had ; but so had Cavitain Skinner, for that was the last we ever saw of the ' Alice ' ! "
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Limiting Improvements in the Small Shop
BY JOHN- H. VAN DEVENTER
SYNOPSIS — Dave Hope tells of the small-shop experiences of two of his acquaintances. One of t,.em was a "stick-in-the-m'id" who became a Cap- tain of Industry; t/.e other, a brilliant but erratic individual, finished up as he began— in a nut fac- tory. This article explains why some of us are not millionaires.
" No, sir ! It's a very promising machine, but I don't want to make it."
Dave Hope was delivering this ultimatum to a young mechanic and inventor who had worked out an ingen- ious device and wanted Dave to manufacture it. The lad had brought for inspection a working model that was beau- tifully finished and that went through its motions in such an unusual yet precise way that no real mechanic could have examine'! it without being interested. In fact, the interest that Dave had displayed and the way that he had fingered the model had raised the inventor's hopes to a high point, and his keen disappointment at the final decision was evident.
" I'm too much of a mechanic to manufacture a machine of that kind, or in fact to manufacture anything at all." said Dave, taking note of the young man's feelings. " That is why I stick to contract work and to making experimental machines to order. No machine that I could manufacture would ever suit me, and I should be adding and improving all the time, which would be fatal to the finances."
" If a good mechanic won't manufacture a good machine, who is a fellow to go to ? " asked the inventor despondently, reaching for his model.
"Wait a bit — don't go yet," said Dave. "I want to tell you about Jones and Jenks; perhaps it may help to answer your question.
ALBERT JONES, THE NATURAL IMPROVER
" Albert Jones was one of the smartest mechanics that ever lived. It came natural to him to improve things, and when he was in a shop he was always suggesting bet- ter ways of doing things. At night he'd spend his spare time thinking up new machines and making sketches of them, just for fun, throwing them away after they were all completed.
" Al got a job as ' improver ' in a big shop. He was right at home at this work and made himself valuable. One day, perhaps, he'd be figuring a new way to chuck pistons and the next be sketching up an attachment to convert a drilling machine into a die sinker. Variety was his spice of life, and he never had to do the same thing twice.
'' A man who lived as quietly and got as good pay as Al did couldn't help but save money, and after a few years he had a lump salted away so big that it bothered him to decide what he ought to do with it. Finally, he concluded to open a shop of his own and start manu- facturing.
" The day after he had arrived <it this decision he was called into the blacksmith department to scheme some way of keeping nuts from bouncing off the helve-hammer bolts and to prevent the bolts themselves from breaking. He sat up until 3 a. m. the next morning, scheming and sketching and scratching his head, and finally invented a shock-absorbing locknut. The following day he quit his job and filed a patent application.
" That locknut was the. best thing of its kind that ever was. It would hang on like a suffragette, and its shock- absorbing qualities were without equal. A mighty good thing to start a manufacturing business on, was that nut, because it could be made in three operations by the crudest kind of help and sold for a price that was an inducement, even if it hadn't had such good qualities besides.
AL GETS BUSY WITH PATENT LOCK NUTS
" Al had his plant going two months before the patent was issued and was forced to add a couple of men every week to keep up with the demand of a public that was hungry for shock-absorbing locknuts. In six months he had designed and built special machines that would turn the nuts out almost as fast as a boy could carry them away. Things looked very rosy indeed for Al — to an outsider.
" There was one big defect in it from his point of view — the thing couldn't be improved upon. It was so simple and perfect that nothing in that line could be any better. An ordinary man would have been very well pleased at such a state of things, but not Al. All of the inventiveness and ingenuity in his system was corked up, so to speak, and was building up a pressure that was bound in time to blow the cork out — that cork being the shock-absorbing locknut ! He began to detest the sight of one. ' Why should a man with brains tie him- self up for life to a dinky one-piece contraption like that ? ' he would ask himself. Then he would lay off for the rest of the day, go back to his room, put his stock- ing-clad feet on the radiator and dream of complicated mechanical stunts that would make an ordinary man dizzy to think about.
WILLIAM JENKS PARTS WITH TEN THOUSAND PLUNKS
" Al was a man who had to act quickly when an idea struck him, so he sold out his shock-absorbing nut busi- ness to a boob by the name of William Jenks, who had as much inventive ingenuity as an Eskimo's totem pole, but who seemed perfectly satisfied to give $10,000 for a business worth five times as much. Then our inventive friend turned himself loose again like a colt in a pasture and began to put lines on paper and take a fresh interest in life.
" The result of his mental cyclone was a patented adjust- able universal reamer that had a range of something like an inch in diameter for one tool as against the ordi- nary range of adjustment which begins with a decimal point followed by a naught. Where the locknut had been but a one-piece article, this tool had 27 parts, not
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MAKING SMALL SHOPS PROFITABLE
counting the screws, and therefore looked 37 times as good to Al, who saw plenty of opportunity for improve- ments and evenings filled with enjoyable mechanical meditation.
" It .took considerably longer to put the reamer on a paying basis than it had to make a go of the locknut. In fact, it cost Al so much money to start things and improve them a bit that he was forced to take in a part- ner — a mean man of money without high mechanical ideals, whose motto was, ' Let well enough alone ! ' Of course, Al couldn't work in harmony with a dub of this kind, so in a year he sold his interest to the dub for $5,000 and breathed freely once more.
A VERTICAL LATHE FOR SHAFT TURNING
" The next venture of friend Al was a duplex lathe that would turn two shafts at once and which, to save room, stood in a vertical position instead of horizontal. Al said that, while there were a number of vertical machines for chuck work, the vertical center-work field needed con- siderable improving. He produced a design that had several original features, one of them being the feed screw that was exactly in the center of the tool carriage, this latter sliding within the body of the lathe, a pair of headstocks and tailstocks being arranged on each side. He had quite a bit of fun improving this machine, espe- cially in getting oil to stay in the vertical headstock bear- ings. By the time the sheriff came to the rescue and the last balance sheet was struck, Al came away with $2,500 and a sense of relief at the prospect of tackling something new.
" One of his friends told him that if he wanted a chance to let loose the full power of his wonderful improving ability he should get into the automatic game, where there was a chance to pull off something big. This sounded pretty good to Al; but $2,500 wasn't enough to break into the automatic game with, so he decided not to manufacture the machine, but. to design one and get somebody else to build it.
" He had considerable trouble with his landlady, who insisted on getting into his room once a week to pick the papers off the floor, she being afraid to let them accum- ulate for a longer time than that because of the fire- insurance policy. This upset the inventing process badly, Al needing one or two days after each weekly clean-up to get the papers back on the floor again in their proper order. In spite of this, after a year of scheming and scratching he had an automatic machine that had more improved features than anything made before. It wasn't hard to get a patent on such an original batch of improve- ments, and a few months later, armed with official docu- ments from Washington, Al started out to find a builder.
FINDING A BUILDER FOR THE SUPERAUTOMATIC
" He called on a man in the automatic business and explained in detail how superior the Jones superauto- matic was to the machine produced by the company. He not only told .it, but proved it, convincing the engineers and experts who were called in to examine the plans. Evi- dently, the Jones superautomatic would be a clean sweep ! Al was told to leave his plans and to call again in a week.
" He was received very cordially by the president. ' My dear Mr. Jones,' said this gentleman, ' we will offer you an exceptional contract for your invention. We wish the exclusive right to this and all improvements that you may make and in return will pay you a royalty of $500 per machine. At this extraordinary figure we will expect you to act as consulting engineer and give a portion of your time to improving this device. Sign here on the bottom line ! '
" I hardly need to say that Al signed. The president's words about ' improving ' were even a stronger inducement than the $500 per.
" For several weeks the inventor of the Jones super- automatic lived in the clouds. He worked out all sorts of further improvements and turned them over to the com- pany, which seemed to be rather slow in getting started on the first machine.
" After six months passed in the same way, our friend began to be worried, especially as he was no longer admitted to the plant. He lay in wait for the president one day and accused him of not living up to his con- tract. ' My man,' said this individual, ' go back and read your contract We agreed to give you a royalty of $500 for each machine built and so far have lived up to your agreement absolutely.'
a What the president of the company had really done was to get Al out of the automatic field, where he would have been a dangerous man. His endless improvements would have kept things in an everlasting state of change, just as the man who finds out how to turn lead into gold will make a lot of trouble for everybody, including him- self.
AL JONES GETS A GOVERNMENT POSITION
" The last I heard of Al Jones was that he had a Gov- ernment position with board and lodging, but no pay. He was engaged in making chalk marks on the floor of the harmless ward; and when a visitor to the asylum asked him what he was drawing, he'd say it was an improved automatic automatic-machine-making machine!
" As time went on, the asylum got to be overcrowded and a new building badly needed. Nothing could be done by the state, however, owing to the high cost of legislators, and it remained for a public-spirited Captain of Industry to donate two or three millions for the purpose. Eather a coincidence it was that this money to build a home for harmless nuts should have come from manufacturing shock-absorbing locknuts! But then William Jenks, who gave- it, although a boob, was a good-hearted sort of chap." . ,
Dave paused a moment and then continued with spe- cific advice to the young inventor. " Now, if you want to make a success of your machine, find some man with money, but without ideas, to get back of it and push it."
An Ounce of Invention
The average small shop with the average invention is a case of gamble pure and simple, with the odds 99 to 1 against success. No doubt about this at all for far less than 1 patent in 100 is successful. If you regard your small shop as an investment and run it as such, steer clear of the patent game until you have salted away enough to provide a distinct " experimental fund " that you can afford to lose.
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Using Skill for Capital in the Small Shop
BY JOHN H. VAN DEVENTER
SYNOPSIS — Doing what other people cannot do is one of the surest ways to success in the small- shop field. This article tells of a New England die-sinking shop that is making good on a line of work that requires a high degree of skill. How large-shop experience helps the small-shop owner to operate on sound and systematic lines becomes evident.
When you go into a successful small shop, you are often struck with the resemblance it has to a well-managed department of a large shop. Evidently there are certain earmarks of good practice that apply to small and large
ing obtained his education in an institution richly enough endowed to be able to find better ways of doing things by experimentation, as distinguished from the small-shop man " brung up " in the small shop, who must cut his eye teeth without the aid of a dentist. And so when the ex-large-shop man starts a small shop he is apt to carry in his rnind the memory of the large-shop department and its way of doing business.
The large-shop idea is evident in the small shop of Hollander & Johnson, Worcester, Mass., who specialize in drop- forge die sinking. At present some seventeen men are employed in this shop, which is a rather rapid growth from a two-man beginning made three years ago. To some extent the demand for drop-forge dies for munition mak-
FIG. 1. A THREE-YEAR-OLD DIE-SINKING SHOP.
shops alike. Some of them, such as a clean floor, orderly and convenient arrangement of machines, proper cup-< boards for small equipment and tools, may be classified, inventoried and written down in plain figures; others are more vague and elusive, but can nevertheless be quite plainly felt by a shopman's sixth sense. Among these is the perception that the work is being handled to advan- tage, from both the customer's and the shop owner's view- points. Time study would paint this picture after a month or two — :the sixth sense will do it instantaneously, tike a " snapshop " photograph.
The small-shop owner who has had a part of his train- ing in a large shop is somewhat ahead of the game, hav-
ing has been responsible for this enlargement; but the start in the right direction was independent of this con- dition, and it is the start that will interest other small shops having a large capital of skill and a small capital of cash.
A shop struggling for a start cannot pick and choose the class of work that it does. Often the crucial test comes in the shape of an order for work that is apparently unsuited to the machine tools at hand. In this case it was an order for 450 sets of molds for making rubber shoe- soles. There were two machines available for this work — a shaper and a die sinker — in fact, with the addition of a lathe they comprised the entire shop equipment. Taking
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MAKING SMALL SHOPS PROFITABLE
the order for these 450 molds for delivery in 6 weeks took both nerve and hard work; but the task was accomplished by operating night and day, and doing it put the small shop on its feet — one might say a pair of rubber-soled ones!
S. G. Hollander obtained his large-shop experience in drop-forge dies at the United Shoe Machinery Co.'s plant
FIG. 2. SINKING RIFLU BOLT Dli^S
at Beverly, Mass., where he had charge of this class of work, both as to making the dies and using them. He has retained one very important large-shop feature in the mak- ing of such things — the division of labor according to the degree of skill required. Some small die-making shops are run on the old toolroom basis, one skilled man travel- ing about from machine to machine and taking care of the job from start to finish. The large-shop method is to pass the work from one man to another, each one a specialist on his own machine or bench, and this scheme is applied in the small shop to good advantage in both time and money.
The properly run small shop can take work requiring a high grade of skill at very nearly the cost-to-make in
FIG.
MOLDS FOR MAKING RUBBER HEELS
the big-shop toolroom and como out with a profit. Here lies one of the big weanons of the small shop in hunting for business, and it is due to the low overhead expense as comrared with the high one in the big plant. A shop of fifteen to twenty men, in which the owner is superintend- ent and manager, correspondent and time clerk, as well as on frequent occasions a die maker or tool maker, will show
up an overhead of from 15 to 25 per cent., as compared with the 100 to 150 per cent, of the big shop. If this fact is thoroughly mastered, it will open up new business for the small-shop man who grasps it and uses it as a selling argument.
• Another feature that will result in business is to relieve the large shop of responsibility and detail. Some people cannot get enovigh responsibility to suit them, but the real big fellows have a habit of placing it on otheir
A
Kid. 4. ARTICLES PRODUCED IN SMALL-SHOP MADE DIES A — Military riflfi forcings: B — Rubber die products; C — Auto and bicycle fcn-fUna? ; D — Bayonet forgings ; K and F — Machine-gun forgings; G — Miscellaneous.
shoulders than their own when they make sure that these shoulders are broad enough to carry it. The small-shop man with small views is apt to pin the responsibility as closely to his customer as he can, living up strictly to his blueprint. The small-shop man with big views goes at it another way, saying: " Show me the piece you want made and the machine on which you want to make it and leave the rest to me. I will be responsible for the result."
(6)
Finding the Turning Point in the Small Shop
BY JOHN II. VAN DEVENTER
SYNOPSIS — In the majority of successful shops there is one definite turning point at which a start is made toward bigger and better business. Many times this change is made unconsciously, and the turning point cannot be definitely located. In 'this case tlie installation of one machine changed the shop product from an average to an excep- tional one.
A small shop that is 68 years old is something of a rarity and is therefore of interest in a country where plants mushroom over night as if under the spell of Aladdin's lamp. That a small shop can stand the buf- fetings and trials of 68 years of competition is also an interesting fact, establishing as it does that the small shop is after all of a hardy and robust nature. In an
FIG. 1. THE LABORATORY OF A SMALL SHOP THAT SPECIALIZES IN HIGH-SPEED STEEL
instance of this kind, one is apt to look for work a little out of the ordinary in order to account for such a long existence.
Knife grinding in the old days before the advent of the surface grinder and the magnetic chuck was an opera- tion in which the old-fashioned grindstone and sidewheel labored in partnership with a patient grinder hand who was unable with all his skill to grind anything really straight. Fifteen-thousandths of an inch was considered a close job in those days. Most of the work was held and fed by hand, some of it in crude fixtures that were as likely to spring the knife out of shape as to hold it flat. Only those who have surface-ground thin stock by such means in the past can appreciate the real value of the magnetic chuck.
Prior to 1906 this was the way that A. Hankey & Co., Rochdale, Mass., were grinding knives. A rather ordi- nary line of work, one might say, and one that was not at all uncommon throughout New England, where knife grinding in America was indigenous.
A shop, in order to keep up with the times, must not only study its own rrogrcss and that of its commtitors, but — and more important — it must keep in close touch
with the progress and tendencies of its customers. Shops exist that are so bound up in themselves that self-interest is a far bigger factor than service, and other shops depend- ing on these for a part of their products oftentimes find their own advancement hindered through a lack of someone's else initiative. At the time of which I have been speaking, when knife grinding was so crudely handled, a class of knife users of considerable importance consisted of the woodworking-machinery manufacturers. Compared with the present-day product, wood planers at this time were crude and slow machines. A feed of 25 ft. per min. was considered high and in fact was about the maximum that could be used for smooth worlj. Any- thing faster than this would show revolution marks 011 the finished board, the old four-square planer head with its thick, clumsy, hand-ground knives being almost impos- sible to balance perfectly.
One could not, without clairvoyant power, foresee that the 25 ft. per min. feed would some day be multiplied twelve times and that lumber would be shot through these machines at the rate of 300 ft. per min. But it was pos- sible to arrive at the conclusion that an improvement in planer knives would mean an increase in planer feeds. Here was an opportunity for some knife-making shop to analyze conditions, find the weak point and help to push aside .the obstacles holding back the progress of the wood planer.
The installation choice of a new machine is taken more seriously in the small shop than in the large one. No doubt this is because one machine among many does not affect the whole as much as when one is added to a few, just as a single vote in a small town is of much more relative importance in local elections than one vote in a large city. The installation of the wrong machine in a big shop means annoyance and a small loss ; the installation of the wrong machine in the small shop may put it out of business. On the other hand, not buying a machine that is needed, while it will not result in a sudden calamity, is likely to terminate in a case of gradual dry rot.
The " Rogers Boys," as J. R. and Francis P. Rogers, Jr., are known in Worcester and vicinity, believed that a suitable surface grinder would solve a problem of the wood-planer knife. Not only had they the conception of what was needed, but not finding a suitable machine for this purpose on the market, they designed and had built the special machine illustrated in Fig. 2 — an act that involved playing a $10,000 stake against their belief. That this was an investment and not a gamble is evi- denced by the fact that from this machine came the first high-speed steel wood-planer knife made, and others have been coming from it ever since.
This machine is of interest, not only as an example of good judgment displayed at an opportune time, but also for what it will do. The grinding wheel is 24 in. in diameter with an S^-m- face. Running at 5,000 ft. per min. it is so free from vibration that one cannot tell whether or not it is in motion, even when holding to
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MAKING SMALL SHOPS PROFITABLE
his ear a screwdriver with its end applied to the wheel bearing.
The table of this machine is 10 ft. long, its entire length being equipped with Walker magnetic chucks having a width of 8% in. There are two table speeds — 40 and 60 ft. — • one for roughing and the other for finish- ing. Oh the class of work produced on this machine, limits and finish are held exceptionally close, some knife specifications calling for tolerances no greater than 0.00025. In view of this requirement the accomplish-
you consider where the price of high-speed steel is today and where it is quite likely to go, there may not be much to be wondered at after all. The accumulation of dirt shown in the tank at A in Fig. 1 is in reality high- speed steel grinding dust floating on top of water. This material is carefully saved, packed and shipped to the steel mills, where every bit of tungsten is eagerly wel- comed.
One can get an idea of the proportions of a high- speed steel wood-planer knife from the illustration at A
FIG. 2. THE SURFACE GRINDER THAT PROVED TO BE THE TURNING POINT
ment of this machine in removing %2 in. per hr. from a surface of 120 in. long and 8l/z in. wide is rather remark- able. The table is reversed by a pneumatic clutch.
The rear view of this machine, seen at B, displays 2J/2-in. flexible steel hose through which cooling water is applied to the wheel. When the machine was first tested out, this hose was not fastened as securely as is shown, but was held by a husky negro who directed it upon the back of the wheel. The gentleman, becoming absent-minded during the course of events, allowed the nozzle to deviate from its proper path; as a result the 2V2-m, stream projected between the housings and knocked a couple of interested spectators from a bench alongside the table. What happened to the spectators is known, but what happened to the darkey is not related.
One does not see anything unusual in the practice of saving the sweepings from the floor of a mint in which gold coins are being made, but it is rather strange to find a similar practice in a knife shop. However, when
in Fig. 3. They are from % to %6 in. thick, from 1% to 2 in. wide and from 4 to 50 in. long. The heat-treat- ment and straightening of a high-speed steel blade of such proportions require a high degree of skill. All these blades are hardened in Kenworthy furnaces using fuel oil vaporized by steam under a pressure of 125 Ib. and are quenched in Houghton's soluble quenching compound. After quenching, -they are tempered, or "let down," to approximately 600 deg. F. Before this, how- ever, they must be straightened, a peculiar thing about high-speed steel being that it is impossible to straighten it after this second heating.
PLANING IRON AT 230 FT. PER Mm.
The machine-shop man who has been unpleasantly sur- prised by the ease with which some high-speed drills and reamers break under slight provocation would expect a thin high-speed steel knife of this kind, hardened to a scleroscope hardness of 85, to be a rather delicate and fragile tool. He would change his mind if he could see
(8)
FINDING THE TURNING POINT IN THE SMALL SHOP
the piece of 1%-in. angle iron shown at B in Fig. 3, which was accidentally fed into a double surfacer and planed both top and bottom for 18 in. of its length at a speed of 230 ft. per rain., some % in. in depth being removed from one of the ribs and a full %z in. from the entire surface of the other rib. The high-speed steel knives which did this fast iron planing were some- what dulled, to be sure, but a grinding put them in condi- tion for further cutting — of lumber.
Before the installation of this " turning-point machine " the Hankey company was doing what a number of other firms were also doing and in about the same way. The use of this machine upon high-speed steel knives, how- ever, necessitated careful study of the heat-treatment of this material and led to a specialization in accurately ground high-speed steel knives and tools, which has been
Weighing Patterns and Castings by Their Displacement of Water
BY W. H. SARGENT
The writer was puzzled to know how to find the size of a pattern for a scale weight the casting from which was to weigh a certain definite amount. The pattern was of such irregular shape that its volume could not be accurately computed, and it was not possible to take off a trial casting. In my trouble I remembered Archi- medes and his stunt with the king's crown, and I thought if I could find the weight of a quantity of water equal in volume to the pattern, then the casting would be to the pattern what the weight of iron is to the weight of water. I punched a hole through the side of
FIG. 3. HIGH-SPEED STEEL, WOOD PLANER K NIVES AND WHAT THEY DID TO ANGLE IRON
a tin can near the top, filled it with water to that point and immersed the pattern. I caught and weighed the water that ran out, which was, of course, equal in vol- ume to the pattern. Multiplying the weight of my " water casting " by the specific gravity of cast iron gave me the corresponding weight of an iron casting.
FIG. 4. COMPOSITE-STEEL WOODWORKING KNIVES
a profitable line of business. But the turning point was the installation of the grinder.
High-carbon and composite-steel tools and knives are also heat-treated and ground at this plant. Two of these are shown in Fig. 4, the one at A being a wood-planer knife for a square-cutter head and the one at B being a miter knife. They have soft steel backing on tool-steel edges. The furnace weld is rolled, and the grinding of a piece of this kind, one part of which is soft and one part hard, without leaving a mark at the junction of the two pieces may be considered a noteworthy job. In fact, the face of these blades must be ground to a radius, that is, held to very close limits. One and one- half thousandths is allowed for location of this radius centrally with the blade, and 0.001 in. is allowed on the length of the radius.
It is not often that a small shop is able to change the grade of its product as markedly as this, owing to the installation of a new machine. Every small shop, however, can keep in mind the fact that each machine installed should be a turning point toward better work and more profits.
This thought, coming at the time when new equipment is to be purchased, will influence the buyer to select the machine best suited to his needs regardless of what its cost might be.
WEIGHING BY PROXY
Another practical application of this principle is find- ing the weight of a casting when no scale is at hand large enough to weigh the casting itself. Fill a pail or tub exactly full of water. Immerse the casting; catch and weigh the water that overflows; multiply the amount by the specific gravity of the material and you have the ' weight of the casting. Thus a casting of nearly 200 Ib. can be weighed " by proxy " on a 25-lb. scale with a consider- able degree of accuracy.
(9)
Spring Fever in the Small Shop
BY JOHN H. VAN DEVENTER
SYNOPSIS — This is a" Dave Hope " story, telling how the inmates of his small machine shop were afflicted with spring -fever and how they were cured l)y inoculation.
There is a disease not mentioned in the medical books. It spreads its influence broadcast over the country each year and spares not rich nor poor, young nor old. It affects most strongly those whose occupations keep them within doors and is a disease that every machinist's appren- tice and even the machinist himself suffers from each year. The germs of this disease are frozen up and harm- less during the winter season; their busy time is the month of May:
When the buds beg-in to blossom
And the bees begin to hum ; When you feel like playing 'possum
And your job seems on the bum.
It is at this season of the year that the machinist in the large or the small shop picks out a soap box or nail keg as a resting place from which he can with the least effort observe the slow progress of the thirty-second-inch feed crawling over the surface of the work. But while his eyes are on the machine, his thoughts are elsewhere. In imagination he is feeling the warmth of the sun upon the back of a neck that has been protected from sleet and storms for many months by an upturned coat collar. He is imagining the satisfaction of indulging his five senses, individually and collectively, with the sights, sounds, smells, tastes and feelings of a rejuvenated earth. And just about the time when his imagination takes him to the crystal-clear inland lake crammed with fish as hungry as starving wolves — bang! The whole thing is punctured by the sarcastic voice of the boss : " Get rid of that hook- worm and double up on your feed ! "
SYMPTOMS OF SPRING FEVER IN DAVE'S SHOP
There were obvious signs that this spring malady had attacked Dave Hope's small shop. One convincing symp- tom was evident in Sandy McPherson's location out of doors, for he had moved the portable work bench from within and was doing his filing under the sky instead of under the shop roof. Eeddy Burke, whose duties con- fined him to a close proximity to machines not so easily portable, looked rather disconsolate. As for the boy and the half-dozen other men who comprised the personnel of the shop, the evidence of the disease was unmistakably written upon them and displayed in every motion.
Dave Hope had not overlooked these indications and, in fact, felt some of the symptoms working in his own system. " This thing is going to cost us some money," he reflected, "because the trouble is sure to last for two weeks at least. During this time one after another of the boys will be taking a day off now and then, and it isn't in my disposition to tell them no, for I'll probably be doing the same thing myself." Just at this moment his eyes rested upon the magazine section of the preceding week's Sunday paper, which happened to lie open at an article entitled " How Disease Is Made Harmless by Inocu- lation." " By George ! " exclaimed Dave to himself ; " I
wonder if there isn't a way to inoculate against spring fever."
He read the article with considerable interest and found that the principle of inoculation is to treat the system with a dose of the disease bacillus that causes the com- plaint. " Looks like a case of fighting fire with fire," muttered Dave, lapsing into a period of silent reflection that lasted several moments. Then he got up, slapped the desk with his fist and ejaculated, " By George, I'll do it!"
DAVE GETS READY TO TRY THE INOCULATION
Next morning Dave did something that it was very unusual for him to do; he lined his men up and made a speech to them. Perhaps it should be called a talk rather than a speech, for there was nothing formal about it any more than about Dave himself.
" Boys, we're all coming down with a bad case of spring fever. I've got it myself, and I know that you have. And I don't blame you for it. But there are some orders here that we've got to get out — that 12x12 engine for Jones' sawmill, the road roller for the town and that duplex pump for Tim Ebbets. Now I'll tell you what we'll do — you boys pitch in and clean these up by Friday night, and we'll shut down until Monday morning, with the condition that all of us together go out for a two days' camp in the woods."
The speech of an eloquent statesman was never received with any more enthusiasm than were these few words of Dave's. All hands pitched in with a vigor that gave evi- dence of the success of the first inoculation.
STARTING OFF FOR THE CAMPING GROUNDS
On Saturday morning at sunrise the wheels of the one-horse farm wagon creaked under the load of eight men and a boy and sundry equipment in the nature of provisions and camp material. Fishpoles were a prom- inent feature included in this assortment of goods, for every small-shop man is instinctively a fisherman by sec- ond nature. Dave had suggested that the party go on foot, thinking that the spring-fever inoculation would take place more rapidly under such circumstances, but com- promised on a farm wagon without springs.
It was very pleasant jogging along the fresh-smelling country road, and the occasional bumps encountered by the springless farm wagon as it rolled over furrows left by recent freshets did not cause any lessening of the enjoyment, unless it was on the part of the boy, who was jolted off the back of the wagon by an unusually severe bump. As the sun grew hotter and the road grew hillier, it was necessary for the party to get out of the wagon and " spell " the horse, who seemed to be suffering from spring fever himself. Coats came off one by one, and beads of perspiration began to bathe newly acquired sunburn. Dave had chosen the road and had taken care to pick one with very little shade.
" Gee," said Tom, the boy, " I didn't think it could be as hot as this in May! "
"Hot, is it?" exclaimed Reddy Burke. " T'ink of the poor byes in Mexico — this is a rayfrigorator be com- parison."
The destination of the campers was an inland stream
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SPKING FEVER IN THE SMALL SHOP
girded by woods. It was a location seldom visited by fisherman, being 18 miles from town and 10 miles from the nearest railroad, and for this reason might be expected to furnish exciting sport and appetizing meals. The coun- try in this neighborhood was sparsely settled, but a farm- house was encountered some six miles distant from the creek, and Dave stopped the wagon to buy some fresh milk and to have a word in private with the farmer.
A RAID ON THE COMMISSARY DEPARTMENT
The two days' supply of eatables in the commissary department had begun to melt under the attack of nine hungry appetites. " If you lads dinna refrain f rae eatin' the noo, we will have nowt for breakfast the morn's morn- in','' cautioned Sandy.
" We'll have fresh fish for breakfast anyway," replied Bill Evans ; " there's a dozen breakfasts and dinners too, swimmin' in that there creek."
Upon arrival at the destination the horse was unhitched from the wagon and tethered in a shady patch of woods. Fishpoles were hurriedly sorted out from among other contraptions, Reddy Burke finding difficulty in unearth- ing his from beneath the big fly tent that had been brought along for sleeping quarters.
There was a rush for strategic positions on the bank of the creek. Sandy McPherson was the first to get into action, baiting his hook with a " night walker " the size of which insured an ambitious catch if any at all. Two minutes later, while Sandy was lighting his pipe, a fero- cious and unexpected pull yanked the pole from his left hand. It was a steel pole, and not having the buoyance of the more common wooden kind, it disappeared beneath the surface, followed by a shower of Scotch impreca- tions.
" Hoot, a beastie wi' sic a pu' can be nae less than a hippopotamus," exclaimed Sandy, after he had cooled down a bit.
This experience heightened the anticipation of the rest of the party, proving as it did that there was big game in the creek. And in confirmation of this, Reddy Burke's pole began to bend vigorously. " Begorry, I hov the baste," exclaimed Reddy, " and it's mesilf that will bring the cray- tur safely to terry firmmy."
REDDY BURKE CATCHES A BIG ONE
Then ensued a momentous struggle between an excited Irishman at one end of a fishpole and a fish of unknown species at the other. The battle waged with varying suc- cess for a half-hour, the rest of the boys dropping their poles and offering varied suggestions as to the best way of landing the catch. Finally, human skill aided by the elasticity of a fishpole conquered. " Get ready to hov a look at the biggest fish in the counthry," exclaimed Reddy, shortening up on his line. But it wasn't a fish — -it was a gigantic snapping turtle.
That place seemed to be the headquarters of the snap- ping-turtle trust. One after another received promising bites, only to find them given by these hard-shell creatures who monopolized the stream. So many hooks were lost in this pastime that the fishermen discontinued their fishing and sought the shade of near-by trees.
The noon repast finished up most of the provisions. It was followed by a nap for all of the party but Dave, who seemed to have business back in the woods. So soothing was the outdoor air of spring that, when the
amateur campers awoke, it was after 6 o'clock and they were as hungry as wolves. By unanimous consent they started for the wagon. But when they reached the clear- ing where it had been left, there was no sign of either horse or wagon!
MYSTERIOUS DISAPPEARANCE OF BOARD AND LODGING
" Sure, 'tis a likely place for the fairies," exclaimed Reddy ; " but if they bewitched the baste and the wagon, they've left tracks behint thim to indicate it." Here he pointed to unmistakable wheel and hoof prints. " Some dhirty rascal has cabbaged the commissary department! "
They succeeded in following the tracks as far as the crossroad, but here the wind had obscured the marks and the men were not enough skilled in wood craft to detect which branch had been taken. Besides, it was grow- ing dark, they were without shelter, and the evening breeze began to feel chilly.
" The best thing for us to do," advised Dave, " is to find some barn where we can sleep. The nearest farm- house is six miles away, and I suggest that we follow the creek road, where we may find something nearer."
A six-mile walk without supper did not attract the rest of the boys, and it was agreed to try the creek road. It was quite dark by this time, and everyone had parted with his last bit of good nature. Tom, the boy, appar- ently could see in the dark better than any of the others. " There is a building over there, I think," he exclaimed, after the party had trudged a half-mile by starlight. " If you fellows will wait here a minute, I'll go over and see what it is."
He came running back in a few moments. " It looks like a good place to sleep," said he; "it's a shed with a lot of sawdust on the floor."
REDDY BURKE HAS A NIGHTMARE
Reddy Burke woke up two hours later from a night- mare in which he, a morgue and a slab of ice played the principal parts. He found that he had sunk downward quite a bit in his bed of sawdust, and he was surrounded with icy cold water. "Wake up, lads," he bellowed at the top of his voice, " the creek is rising and youse will all be drownded ! " Someone struck a match, and by its flicker they could see that they had gone to sleep in an ice- house !
Two hours later the moon looked down on a discon- solate party trudging back toward town. It was almost dawn when they came to the farmhouse where the milk had been obtained. " Guess I'll run in here and see if the farmer has seen anything of our horse and wagon," said Dave.
He did not have much trouble in arousing this gentle- man, who led him back to the barn and the missing con- veyance. " Wall, I reckon you're satisfied that I followed directions all right enough, aint ye?" said the farmer, with a sly wink as he pocketed Dave's two-dollar bill.
The horse ambled along with his load of homeward bound pilgrims, quite unconscious of the verbal abuse that was heaped upon him by men who were too tired to sleep and too angry to converse.
Sunday was spent at home in bed by the members of the camping party; and when they returned to work on Monday morning, the spring-fever inoculation was com- plete. Even Sandy McPherson moved his work bench back into the shop.
(11)
Making Patterns and Castings for the Small
Shop
BY JOHN H. VAN DEVENTER
SYNOPSIS- — What to avoid is even more important to know than what to do. This article throws cold water on the ambition of the small-shop owner who is thinking of operating his own foun- dry. Patterns also come in for their share of rapping.
A foundry is a handy thing to have in connection with a big shop — you can blame most mistakes upon it. This abode of the sand rammer has always been a convenient " goat," and many a shop foreman would lose his job if deprived of its unconscious support when it comes to excuses for spoiled work.
When the time clerk trots down the line with a job that took an hour and a half longer than it should, what is more easy and soothing than to tell him that the cast-
unless good, while those that are made must be paid for whether good or bad.
One of the supposed advantages of having your own foundry is in being able to get castings on time, but those who have foundries have come to believe that this advan- tage is not inseparably affixed to them. If the small- shop man is really looking for trouble, let him add the duty of a foundry superintendent and metal mixer to his already numerous and diversified duties and learn the 39 reasons why a casting can come out bad, starting with too high a barometric pressure and ending with too hard sand ramming, and he will feel as if he had his hands full.
There are of course exceptions to this even in the small shop. Some isolated cases exist where a foundry that can take no more than one heat a week will make a profit. But this is due to unusual conditions, such as the absence of competition; and since the majority of our small shops are in fairly close touch with competition, it does not apply in general.
There are some small-shop owners who think to add to their volume of business by adding to the number of
U 10'- *l
Casting Pattern f -^ Casting
W
FIG. 1. TOM COOPER'S EXPERIENCE WITH ROLLS
ing was hard and sandy and that you think some cuss over in the foundry must have slipped a couple of files into the cupola? When the old man sits on your neck because a machine is three days overdue, what will change a disorderly rout into a glorious retreat more quickly than to tell him that the frame pattern was rapped so large that it required three cuts to get it down to finishing size? When a pulley or gear arm has cracks in it, how is it possible for these to have occurred in the casting any- where but in the foundry where it was made? In one large shop with which I am familiar there is a saying as follows : " A slight error in the designing department, a
mistake in the machine shop, ad big blunder in the
foundry."
While a foundry is so convenient in this respect, aside from its capacity to deliver castings, it is usually an expensive luxury when attached to a small shop. When castings can be bought on contract as cheaply as is possible nowadays, it is foolish to assume a new burden of respon- sibility with the prospect of such a slight saving as that between the cost to make and the cost to buy, especially where the castings that are bought need not be paid for
fig
A B C
FIG. 2. TROUBLE WITH NOT ENOUGH AND TOO MUCH FILLET
departments in their plant. Not satisfied with an ordinary machine shop, they must have a foundry, blacksmith shop, pattern 'shop, nickel-plating department and what not. One shop owner of my acquaintance was doing a total volume of business of less than $12,000 a year and yet kept adding one department after another. Most people find it hard to support simply a machine shop on this amount of annual business, let alone extending it over a blacksmith shop, foundry and pattern shop. In addition to spreading the money very thin, the capacity of an ordinary human being must be stretched to the breaking point when he has to look after such a great variety of things. You will find the most successful shops are those that find out what they can do to best advantage and then cut out everything else as much as possible.
The same reasoning applies to making patterns. It is hard to get some men to realize that this is a special trade in itself. Unless a man is in daily touch with foundry conditions, knows foundry problems and has had years of experience with them as well as with his own trade, he is not fitted to make a real pattern. What I mean by a real pattern is one for a piece of work that counts for something, not the ordinary odds and ends of junk required about the shop from time to time, which may be made from whatever is at hand.
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MAKING PATTERNS AND CASTINGS FOR THE SMALL SHOP
Old Bill Higgins, of Vermont, knew these facts as well as anyone and yet insisted on making his own patterns. But then he was a man who ran in unusually good luck. He said that to get a good casting you must have a good pattern ; to get a good pattern you must have a good design ; to get a good design you must have a good designer; and to get such a man you must have a lot of luck, so the whole casting business resolves itself into a matter of luck anyway, whichever way you look at it. Whereupon he would proceed to make a pattern that violated all the laws of nature. He would put the draft upside down and the cores inside out, mold it in too small a flask in the wrong kind of sand, ram it too hard and pour it too cold — and get a good casting !
Sometimes the carpenter finds that it falls to his part to make the small-shop patterns. They tell of one such wood butcher, newly hired by a small-shop owner, who, when told to put a little more draft on the pattern he was making, opened the window in front of the bench a bit wider!
Tom Cooper thought he knew enough to make a pattern for a plain cylindrical roll. He botched together a pat- tern such as shown at A, Fig. 1, allowing M.e-in. diameter
FIG. 3. CAME OUT DIFFERENT EVERY TIME IT WAS MADE
for shrinkage. He sent this over to the nearest foundry with instruction to cast it on end,- so to get the surface clean all around. He was quite surprised on receiving the casting to find that one end of it was larger than the pattern. He jumped on the foundryman for rapping the pattern on this job with a sledge hammer, but got a quick come-back combined with, the information that he should have made allowance for the pressure due to the head of liquid iron, which had expanded the mold at the bottom. After some experimenting,, he found the way to get a straight casting by making the pattern tapered, as shown at B. But he used up several hundred feet of good pat- tern lumber and a lot of time finding this out.
A JOB THAT BOTHERED TOM COOPER
Another little job that bothered him some was a pattern of which there were several -(- sections. Tom first made these as illustrated at A in Fig. 2 and got his pattern back in short order with a request to put fillets in the corners. He did so in the way seen at B and was shocked to find that too much fillet is as bad as too little, for the central portion was so heavy in comparison with the ribs that the unequal cooling set up heavy strains that resulted in cracks. Finally, the foundry owner took pity, on him and told him to make it as shown at C, so that there would be a gradual change in the width of sections from
one part to another. But while fussing around with these things, he overlooked a bad error in a machine for his best customer, and it was shipped without remedying the defect.
Not yet having his fingers badly enough burned, Tom tackled a pattern which had a channel cross-section, like that at A in Fig. 3. This pattern was straight, to be sure, but the casting came to him as hollow as an empty stom- ach, looking quite like the illustration at B. He called up the foundry on the phone, but dropped the receiver in a hurry when the foundry boss told him that he did not pay his men to furnish brains for amateur pattern makers. He sent the pattern to another foundry and got back a casting bent in the opposite direction, like the one shown at C. Then he changed the pattern a bit, thinning the metal at the center and thickening it at the ends. The casting which resulted, shown at D, reminded him of a dog stretching after a nap. In desperation he gave the job to a pattern maker, who solved the problem by thick- ening the ribs as at E.
A mistaken belief is a hard thing to kill, and Tom's
A B
FIG. 4. CURING ONE DISEASE BROUGHT ON ANOTHER JUST AS BAD
belief in his pattern-making ability was not yet dead, even after such a severe shaking up, so he tackled a pulley.
A cast-iron pulley is one of the most innocent appear- ing objects, but beneath its honest sandy skin it contains a heart more full of stresses and strains to the square inch than anything else one can imagine. First, . Tom made the rim light, as in Fig. 4 at A, so that it would not. require a heavy cut for finishing. As a matter of fact it did not require any, meeting its finish while cooling in the sand. Then he made the rim heayy, so that this would not happen again, but unfortunately, with the results shown at B, the arms breaking this time instead of the rim. He lightened the rim a bit and made the arms a little heavier, but found that, although the casting looked good, the arms would snap under the slightest provocation, the hub thickness being much too great for equal cooling. Finally, it dawned upon Tom that he did not know much about pattern making and that it would be cheaper for him to have the few patterns he required made by someone who knew how. ~.
Not only with reference to making patterns and cast- ings, but with almost everything else the following should be remembered : A man can know nearly all there is to know about one thing, he can know a great deal about a few things, or he can know a little about a great many things. Take your choice, but remember that success will come only with the proper choosing.
(13)
The Small-Shop Grinding Wheel
BY JOHN H. VAN DEVEXTER
SYNOPSIS — Although often wrongly selected, incorrectly mounted, improperly speeded and unfav- orably used, the small-shop grinding wheel plays no inconsiderable part in getting out the work. This article is intended as a help to the better understanding and use of this crude but effective shop appliance.
Some day perhaps the creator of " Happy Hooligan " will lead him into a small machine shop and then show us in pictures what happens to him. The old fellow must he getting tired of the regular routine of mishaps and would appreciate something different, such as getting bumped with a planer table or being scalped by a driving belt. But for all-around entertainment let him be intro-
FIGS. 1 AND 2. TWO WAYS OP SIDETRACKING THE VIBRATION QUESTION
one exciting. And mind you, I am speaking of the simple apparatus found in all shops, which consists mainly of wheels and belts — not the " grinding machine " that is nine-tenths machine and only one-tenth wheel. On these simple appliances tools are ground, keys are fitted, cast- ings are snagged, hurry-up jobs are surfaced, that which is too long is shortened, that which is too wide is made narrow, and that which is rough is made smooth. Yet in spite of its broad application, you find in many shops that grinding wheels are more abused than used.
The error that I will attack first, because it is the most common one, is the lack of running balance.
" What's that, an earthquake ? " you ask as you feel the floor beginning to shake and tremble.
" Oh, no," is the reply. " it's just Tom starting up the grinding wheel."
One can hardly stand within ten feet of a grinding wheel in the average shop without feeling the vibrations running up and down his backbone. That this is an entirely unnecessary condition is seen when you consider that plain grinding machines with wheels running at the limit surface speed are practically free from vibration. They have to be, in fact, to produce accurate work. The result is not obtained by sleight of hand, but is due to three simple factors — a substantial base, true spindle and bearings, and well-balanced running parts.
The first essential of a smooth, quiet running wheel is a heavy frame. It is easier for a dog to shake a little tail than a big one. Some shop owners sidetrack the vibration question, in a manner shown in Fig. 1, by attempting to mount the grinding wheel on a springy frame, with the
FIG. 3. FOUR METHODS OF MOUNTING GRINDING WHEELS
FIG. 4. SAFETY COLLAR MOUNTING
duced to a grinding wheel. Picture to yourself the expression of his face after feeling of the wheel with his fingers or upon taking hold of the " heavy " end of the piece of work ! Imagine him trying to light his " snipe " at a stream of sparks. Picture him reclining gracefully against a swiftly moving snagging wheel and then mak- ing a hasty exit with a newspaper held to conceal the damages !
The small-shop owner finds as many ways to make a grinding wheel helpful as a Hooligan would find to make
idea that it will absorb vibration. Considering the amount of work that is expected from a grinding wheel, it should not be begrudged a sufficiently heavy base.
It is not uncommon to find shop owners with the idea that a grinding head may be shaken together out of the crudest kind of material. Bearings and spindles that are shaken together in this manner will continue to shake together as long as they last. The speed at which a grind- ing wheel must run requires not only a smooth, round, true and well-balanced spindle, but also bearings of the
(14)
THE SMALL-SHOP GRINDING WHEEL
most improved design, well lubricated and dustproof, and the spindle pulley must be carefully balanced.
" Shall I use a plain bearing or a ball-bearing grinder head ? " This depends absolutely upon whether you will keep the wheel running true and in balance, or allow it to vibrate. Ball bearings on apparatus of this kind will save power, especially on wheels that are run idle a large part of the time. But there is no make of ball bearing that can possibly live under the hammering punishment of an unbalanced emery wheel.
Grinding wheels when received from their manufac- turers are likely to be in good running balance ; but as the density of the material in these wheels is not uniform, it is quite likely that after one of them is worn down an inch or two it will get out of balance. A means of quickly overcoming this is shown in Fig. 2. It consists of bal- ancing flanges having light spots, which may be placed either opposite or together, or in any other relation to secure the desired counterbalancing effect. The use of such flanges is a mighty good scheme and saves time in making a wheel vibrationless.
While vibration is the most common defect of the grinding wheel, it is not the most important one, if the importance of these things is to be measured by their effects on safety. Bad wheel mountings and lack of guards have been responsible for more accidents than any other causes. I for one would much prefer to stand in front of a cor- rectly mounted wheel running 10 per cent, overspeed than in front of a badly mounted wheel running 10 per cent, underspeed.
Clang! Clang!
" There goes the ambulance. Won- der what's the matter! Oh, it's old Bill from the Triumph Works — he's all smashed up. Emery wheel let go and hit him. They say it broke three ribs and tore off half of his face — mussed him up so you wouldn't know him. Oh, well, such things will happen. Say, ain't this war dreadful ! "
Old Bill will spend the next two months in the hos- pital — if he is lucky or (unlucky) enough to live at all. When he comes out he will be as complete a wreck as any shrapnel-torn victim of bloody carnage. Bill's boss says the war should be stopped — that it's a shame for people to allow such things to happen nowadays. But why did ho allow Bill to run his wheel without a guard and with flanges that were too small? That crime of neg- ligence will stand against Bill's boss as black as many of the war-inflamed atrocities against those who in blind anger perpetrate them. You can't stop the war, Mr. Small-Shop Man, but you can make your grinding wheels safe ! The old excuse that " My work won't allow of a guard " is getting threadbare and won't be presentable much longer.
Grinding-wheel guards have been illustrated so fre- quently in the columns of the American Machinist that I will not attempt to illustrate them here. All reputable makers of grinding stands equip them with guards, and if the stand is a home-made affair the guard can be also. Make the scroll out of % or V^-in- boiler plate, and bolt on side plate as an additional precaution. Keep the inside diameter of the scroll as near that of the wheel as
possible, so that if a wheel lets go, it can't get far enough to work up much momentum.
There are certain principles in connection with mount- ing a grinding wheel which have been found by experience to lessen the risk of breakage. First, the bore of the wheel should be about 0.005 in. larger than the diameter
TABLE 1.
MINIMUM SIZES IN INCHES OF MACHINE SPINDLES
Diam.
in 'n.
6
7
8
9
10
14 16 18
-Thickness of Wheels in Inches
% % i 1% 1% 1% 2 2y4 2y2 2%
I
% %
1
1 1 1 1
1 1 1
1% iy*
1
1%
1% I'/i 1V4 1% I'/i 1% 1% 1% 1%
of the spindle, or in other words, an easy fit. The inner flange should be fixed to the spindle, either being shrunk on and turned in place or mounted as a light drive on a sliding key. Both flanges should be recessed so that the wheel is grasped by the outer edges of the flanges. Blot- ting-paper gaskets should be placed between the flanges and the wheel, and the wheel itself should not be clamped too tightly. These principles apply to any one of the
PEG. 5. KEEPING GRINDING WHEELS AT PROPER SPEED
PIG. 6. BE SURE THAT THE SPINDLE NUT TENDS TO TIGHTEN
four methods of mounting, shown in Fig. 3, of which the most common are shown at A and B, being what are called the " straight " mounting and the " safety " mount- ing respectively. Unguarded wheels should be of the safety type, with flanges so large that the wheel itself does not extend over two inches beyond them. The use of these flanges, however, should not be taken as an excuse
TABLE 2. DIMENSIONS IN INCHES OF TAPERED FLANGES AND TAPERED WHEELS WHERE HOODS ARE
NOT USED IN CONJUNCTION THEREWITH a Maximum flat spot at center of flange, b Flat spot at center of wheel, c Minimum diameter of flange, d Minimum thickness of flange at bore, e Minimum diameter of recess in taper flanges, f Minimum thickness of each flange for single taper at bore.
% 3% %
% 4 %
% 5% %
t7 %
g 1
to do without a guard. The ideal scheme may be said to be to use both precautions, making doubly sure against accident. A well-known form of safety flange is shown in Fig. 4. It is the product of the Safety Emery Wheel Co., of Springfield, Ohio.
Be sure that the wheel rotates in a direction that tends
|
Diam. of |
|||
|
Wheel in |
a |
b |
c |
|
In. |
|||
|
6 |
0 |
1 |
3 |
|
8 |
0 |
1 |
5 |
|
10 |
0 |
2 |
6 |
|
12 |
4 |
4% |
6 |
|
14 |
4 |
«% |
g |
|
16 |
4 |
6 |
10 |
|
18 |
4 |
6 |
12 |
(15)
MAKING SMALL SHOPS PROFITABLE
to tighten, and not loosen, the outer flange nut. Vibra- tion will cause a nut to dance off of the end of the spindle if this precaution is not taken, and it is sometimes annoy- ing to have to dodge the wheel that follows, or to repair the hole in the shop roof left by its exit. The illustra- tion, Fig. 6, shows the proper thread to 'use for various rotations and hands of wheels.
Grinding wheels cut most efficiently at certain definite speeds, depending upon the grain, grade and use. Usu- ally this speed is stamped upon the wheel by the makers, in terms of revolutions per minute. This does very well for a new wheel ; but as work is done and the wheel is dressed, it becomes smaller in diameter, and while the
FIG. 7. ENLARGING THE HOLE
IN A GRINDING
WHEEL
PIG. 8. THINK OF THE
GRINDING WHEEL AS
A CIRCULAR SAW
Waved or Twisted Dresser FIG. 9. PLENTY OF VARIETIES TO CHOOSE FROM
Guard for Wheel Dresser
revolutions per minute stay the same the surface speed decreases and the wheel becomes less efficient. The scheme shown in Fig. 5 is a good one to overcome this drawback in a shop where two or more grinding stands are in operation. As the wheels become smaller, they are transferred to spindles of higher speed. Limit pins are used, as shown, to prevent getting on a wheel larger than is proper for the spindle speed.
A grinding wheel should be thought of as a circular saw. When the teeth are sharp and the cutting speed is right, it removes metal freely. Such a wheel is illustrated diagrammatically in Fig. 8 at A. A "loaded" wheel is shown at B, in which the teeth still remain but have their spaces filled with the material being ground, so that cut- ting is slow. A glazed wheel corresponds to a saw with its teeth ground away, and is shown at C. Very fre- quently the tendency of a wheel either to load or glaze may be overcome by running at a decreased speed. On the other hand, wheels which appear to be too soft are
made to operate correctly by increasing their speed, tak- ing care, however, not to exceed the safe limit.
There is no excuse for the small-shop owner pleading ignorance of good grinding-wheel practice. The Com- mittee Report of the National Machine Tool Builders on grinding-wheel and machine safeguards was published in
TABLE 3. DIMENSIONS IN INCHES OF STRAIGHT FLANGES
AND STRAIGHT WHEELS AND FOR SAFETY FLANGES
USED WITH PROTECTION HOODS
|
A |
B |
C |
D |
|
Diam. of |
Min. Outside |
Min. Diam. |
Min. Thickness |
|
Wheel in In. |
Diam. of Flange |
of Recess * |
of Flange at Bore |
|
6 |
2 |
1 |
% |
|
8 |
3 |
2 |
% |
|
10 |
3% |
2V* |
% |
|
12 |
4 |
2% |
Vi |
|
14 |
4% |
3 |
% |
|
16 |
5% |
3H |
|
|
18 |
6 |
4 |
% |
* Recess to be at least Via-in. deep.
the American Machinist in Vol. 40 on p. 921. An elab- orate table showing the causes of emery-wheel accidents was published in Vol. 39, p. 1060. On p. 129 of Vol. 42 a comprehensive " safety code " drawn up by a commit- tee appointed by the abrasive-wheel manufacturers was presented to the readers. All three of these reports, mod- ified and combined, were presented in one paper l at the recent annual meeting of the American Society of Mechanical Engineers.
The following extracts are taken from this paper:
Before mounting, all wheels shall be closely inspected to make sure that they have not been injured in transit, storage, or otherwise. For added precaution, wheels other than of the elastic and vulcanite types should be tapped slightly with a ham- mer ; if they do not ring with a ' clear tone they should not be used. Stamped wheels when tapped with a hammer may not give a clear tone. Wheels must be dry and free from sawdust when applying this test.
Wheel spindles shall be of sufficient length to permit of the nuts being drawn up at least flush with the end of the spindle, thus providing a bearing for the entire length of nut.
Protruding ends of the wheel arbors and their nuts shall be guarded.
Flanges, whether straight or tapered, must be frequently inspected to guard against the use of flanges which have be- come bent or sprung out of true or out of balance. If a tapered wheel has broken, the tapered flanges must be carefully 'inspected
TABLE 4. REVOLUTIONS PER MINUTE TO GIVE PERIPHERAL SPEED IN FEET. PER MINUTE
|
Diam. of |
||||||
|
Wheel in In. |
4,000 |
4,500 |
5,000 |
5,500 |
6,000 |
6,500 |
|
6 |
2,546 |
2,865 |
3,183 |
3,500 |
3,820 |
4,140 |
|
7 |
2,183 |
2,455 |
2,728 |
3,000 |
3,274 |
• 3,550 |
|
8 |
1,910 |
2,150 |
2,387 |
2,635 |
2,865 |
3,100 |
|
10 |
1,528 |
1,720 |
1,910 |
2,100 |
2,292 |
2,485 |
|
12 |
1,273 |
1,453 |
1,592 |
1,750 |
1,910 |
2,070 |
|
14 |
1,091 |
1,228 |
1,364 |
1,500 |
1,637 |
1,773 |
|
16 |
955 |
1,075 |
1,194 |
1,314 |
1,432 |
1,552 |
|
18 |
849 |
957 |
1,061 |
1,167 |
1,273 |
1,380 |
|
20 |
764 |
S60 |
955 |
1,050 |
1,146 |
1,241 |
(16)
for truth before using with a new wheel. Clamping nuts shall also be inspected.
The work rest must be kept adjusted close to the wheel to prevent the work from' being caught. Work rest must be rigid and always securely clamped after each adjustment.
A speed of 5,000 peripheral feet per minute is recommended as the standard operating speed for vitrified and silicate straight wheels, tapered wheels, and shapes other than those known as- cup and cylinder wheels, which are used on bench floor, swing-frame and other machines for rough grinding. Speeds exceeding 5,000 ft. may be used upon recommendation of the wheel manufacturers, but in :no case shall a speed of 6,500 peripheral feet be exceeded.
A wheel used in wet grinding shall not be allow'ed to stand partly immersed in the water. The water-soaked portion may throw the wheel dangerously out of balance.
Work shall not be forced against a cold wheel, but applied gradually, giving the wheel an opportunity to warm and thereby eliminate possible breakage. This applies to starting work in the morning in grinding rooms which are not heated in winter, and to new wheels which have been stored in a cold place.
1 Copies of this report may be obtained from the A. S. M. E. by mentioning its title, " Safety Code for the Use and Care of Abrasive Wheels," and inclosing lOc. with the request.
The Small-Shop Grinder
BY JOHN H. VAN DEVENTER
SYNOPSIS — Machine grinding is not by any means restricted to large shops. It is true that the average small shop cannot afford to install a specialized machine with a small range of work for this purpose, hut it should investigate the use of grinders of the universal type having a broad range. In this article the problem <is attacked from the small-shop angle, and the causes and remedies of common grinding troubles are given.
The small-shop man does not ordinarily make his acquaintance with the art of grinding on what is called a " grinder." His introduction to this method of remov- ing metal comes by way of a casting snagger, such as was described in " The Small-Shop Grinding Wheel," on
FIG. 1.
SURFACE-GRINDING ATTACHMENT APPLIED TO THE PLANER
page 14 of this volume. This acquaintanceship broadens out through experience with various improvised grinding devices, which are applied at various times to each machine in the shop, from the engine lathe to the planer, usually with more or less unsatisfactory results. Finally comes the ultimate achievement — the purchase of a " tool grinder " — which usually accompanies the advent of the first miller. In the majority of small shops the owner " guesses " that this is as far as it is safe to go in the installation of grinding equipment. Whether this is a good or a bad guess depends greatly on the kind of work that is being done, but I venture to say that it is a bad guess in a great many cases.
' One of the wrong notions of grinding is that its object is only to obtain a fine, smooth, accurate job. In 75 per cent, of the large shops that finish work by this means the compelling object is not the fine finish so much as the reduction in cost that can be obtained over the old method of finishing 'by fussing with fine cuts and a file. Lathe hands will not Start to file on a shaft that is left full of grooves from a roughing cut — it is too
much like work. The grinder has no such notions about the matter, however, and will tackle the roughest job with the same degree of self-confidence that it displays on going over a glasslike surface. One good way to look at the grinder is as a filing and polishing machine, a device that will do the finishing much more quickly and with less need of skill than is required to manipulate the file and emery cloth.
" I don't need a grinder in my shop," says Bill Jones ; " my lots are too small. I seldom have more than six like pieces going through the shop at the same time." By the same token, as the Irishman would say, Bill doesn't need a lathe or any other tool in his shop; for having such small lots, he should hog out the work with vise and cold chisel. You will find someone able to advance the most plausible objections against the use of any improvement that ever was invented, and the old
FIG. 2.
TRAVERSE SPINDLE GRINDER ATTACHED TO THE ENGINE LATHE
excuse of " small lots " is a standby in the shop where progressiveness has taken a back seat in favor of precedence and habit.
It is easier to set up a grinder for an average job than to get a lathe ready for business, and the time saved even on one piece will often overbalance the setting-up time of the additional machine. Work that is similar, such as grinding shafts of various lengths, can be handled with the same set-up simply by moving the tailstock and obtaining a suitable work speed. Where there's a will there's a way; and where a way is found, nine times in ten there is profit also discovered.
The small shop that wishes to cut its eye teeth on the subject of grinding, at a minimum of expense, may do so by means of a tool-post grinder similar to that shown in Fig. 1. The advent of a small and durable electric motor makes this arrangement practical, as it dispenses with long overhead pulleys and traveling belts. An outfit of this kind will convert almost any machine tool into a grinder of sorts. In the illustration, Fig. 1, it is shown applied to a job of surface grinding, in
(17)
MAKING SMALL SHOPS PROFITABLE
which a planer table is used to traverse the work and the planer head to crossfeed the wheel. Such a device cannot be expected to do the work of a machine especially designed for grinding. For one reason, the bearings are less rigid and will in time get loose; but if they are kept in first-class condition and too heavy cutting is not attempted, this tool-post grinder will answer the
the double purpose of grinding the lathe tools and cutting down the time otherwise wasted in walking to and from the regular tool-grinding wheel.
For a more accurate class of work the traverse-spindle grinder, shown in Fig. 2, is applied to lathes or millers with satisfactory results. The accuracy of the grinding, assuming that the fixture is in good condition, depends
!• f f ?
A.X*-,%.X\xyvlV\vVVVCA.A.V<V
WHEEL OUT OF BALANCE BAD BELT JOINT (TRUE AND' BALANCE ...... (MAKE ENDLESS)
If NKESSARY) **m \ SIDE PLAY
WHEEL TOO SOFT
(TRT A HARDER
ONE)
SIDE PLAY OF BELT
ir*— -(TIGHTEN BELT)
iii« iiiii|iini Hiiiiiipiiiiii mnui
A DEPTH OF CUT TOO GREAT
/T-OV A TKQUTCD riKIT^
CENTER HOLES
TOO SMALL (REDRILL THEM)
. LOOSE BEARINGS -;;;----;(TAKE UP)
EPTH OF CUT TOO GREAT (TRY A TIGHTER ONE) ^ ^
BY WHEEL
DOG SET ON! LKUNt' WORK SET IN VIBRATION
AN ANGLE WORK SPEED TOO HIGH BY WHEEL
(CUSHION WITH ("UN SUWO) (USE STEADY RESTS)
BELT LACE) COUNTERSHAFT OUT OF BALANCE
(TEST AND REBALANCE IT)
I/Ill "Hill" ••<,/!•• •'"'//'" ""/
!IDDLE OF WORJCOUT OF ROUND OR SIZE
'Hii' -""iiiimiiiiiiuii" ••""iiiiiinii" ^j
C
nW "»\\\\v. >\\\\\4
J..ENDS OF WORK OUT OF ROUND
mtiDDlh' ••"iilimii "HI
DEAD CENTCR WORN OUT OF ROUND ---> (REGRIND)
WORK LOOSE BETWEEN
CENTERS —(ADJUST TAIL CENTER)
TAPER ON STRAIGHT WORK
WHEEL REDUCED IN DIAMETER DURING TRAVERSE
(REDUCE DEPTH OF cur)
DIRT IN DEAD CENTER BEARING — (CLEAN OUT CAREFULLY)
.ilt||||||i. I.-1"
llllni.
CAM
HEAT STRAINS (TURN ON i
MORE WATER)
INTERNAL STRAINS IN THE PIECE (ANNEAL)
KIIHKi mnmim......
WORK OUT OF BALANCE
(DEDUCE YIORK SPEED AND
APPLY STEADY REST)
FIG. 3.
CAUSES AND REMEDIES FOR MANY OF THE COMMON GRINDING TROUBLES MET IN BOTH SMALL AND
LAKGE SHOPS
purpose on the occasional job that cannot be handled by any other means. A grinder of this same type does excel- lent work in the lathe, if the precautions necessary to be followed in doing the same kind of work on a regular grinder are observed.
In many shops it is considered sufficient to stick the motor-driven grinding wheel in the tool post, put long slender work between centers and start to cut. In such cases it is usual to run the work speed well beyond the limit required for turning the same diameter, and also to use a hard close-grained wheel. When the job is finished, the boss wants to know who has been hammering at the shaft and has put in all the flat spots that are plentifully distributed over the surface of the work. A much softer wheel, a work speed one-third that required for a high-speed tool cutting on similar material and the use of back rests supporting the work from the back and from beneath on shock-absorbing wooden blocks will give quite different results.
A portable grinder of this kind can be used all around the shop. On the miller it will grind a fresh edge on cutters without removing them from the spindle; and when no other pressing use can be found, it can be bolted to the vacant end of the lathe bed and made available for
solely on the truth of the headstock or miller spindle by which the piece to be ground is rotated. An outfit of the kind shown is inexpensive and will handle the most accurate work. It is driven from overhead, usually by means of a round or twisted belt, and necessitates the use of a drum pulley for this purpose, unless a small motor equipped with a driving pulley is mounted on the same slide.
One of the peculiar things about a traverse-spindle grinder that its operator must learn by experience is that the bearings are not in proper condition unless they run hot. If they do not, it is a sign that they are too loose for an accurate grinding job to be obtained. When you can rest your finger with comfort on the bearings of a contrivance of this kind, there is something the matter with it!
A grinding device of this simple and inexpensive type is suitable, not only for internal work, but also for angular and external work, since it can be swiveled about to any angle. In spite of its apparent lightness and the small dimensions of its spindle and bearings it will handle a very respectable cut in hardened steel.
The universal grinder presents itself as the next step in advance for the small-shop man who has outgrown
(18)
THE SMALL-SHOP GRINDER
the use of the foregoing expedients. It is true that a machine of this kind costs considerably more than a simple tool grinder that may fill the bill for some time after its purchase. On the other hand, the range of work of a universal machine is so great that this must be taken into consideration and weighed as a part of the value received per dollar expended. A machine that costs $800 and that is capable of earning $8,000 during its life of usefulness is a much better investment than one that costs but $200 and can earn $1,000. In the case of the universal grinder you have as an asset its capability of handling commercial grinding, not as rapidly, of course, as it could be done on a plain machine of the same capacity, but fast enough to bring in a good profit. Such a machine should always be equipped for wet grinding.
This type of tool will handle not only all the grinding requirements of the small-shop tools and cutters, but also its commercial precision grinding — internal, external and angular — and a good range of commercial cylindrical and taper grinding in addition. In the average small shop it will be a long while before the demands for com- mercial work on a machine of this sort exceed its capacity in spare time. When such a time does arrive, it will be sufficiently soon to investigate the plain grinder as a means of handling this work.
WET OR DRY GRINDING
The question of " wet or dry " is an absorbing one to the citizens of many of our states, where the matter is eventually settled by ballot. When it comes to grinding, opinion is more unanimous and is quite in favor of " wet." The use of a lubricant, or rather " coolant," on the grinder helps to make quick time and to give a smooth job, but its main purpose is to prevent the distortion that would otherwise occur, due to heating. When you consider that the chips torn from the work in grinding are raised to a temperature corresponding to the welding point of steel, the subject of temperature and the need of a cooling fluid take on a new importance. Oftentimes the water attachment is dispensed with as being a mussy contraption, a green hand finding that he needs a bathing suit more than a micrometer to help him navigate a grinder. This is all wrong and unnecessary ; for if the stream is properly directed against the work, there will be absolutely no splash.
Among the things to keep in mind in operating a grinder is to use work surface speeds ranging from 25 to 35 ft. per min. when roughing, and 25 per cent, faster for finishing. As soft a wheel as possible should be used for the job, and the traverse per revolution should be between five-eighths and seven-eighths of the wheel face, in order to prevent wearing away its edges.
Some of the most common grinder troubles are repre- sented in Fig. 3, which gives their causes and also the remedies to be applied in getting rid of them. They arc included in this article, not to dishearten one who is contemplating the use of the grinder, but as a help for those who already have such machines. The former must remember that even in a foundry there are forty-seven ways of making a bad casting and that the comparatively few causes of trouble on grinders are really a recom- mendation for this type cf machine.
A Handy Clip for Hanging Wet Blueprints
BY E. H. GIBSON
Draftsmen will agree that the market has little to offer in the way of a convenient device for hanging! blueprints to dry. Except in the case of such draft- ing rooms as are equipped with elaborate drying and ironing machines, little consideration is given to the
|
u jy BLUE-PRINT |
*=tf==w= =y; BUIE-PRINT |
WOOD CLIP FOR HANGING BLUEPRINTS
matter, the problem usually being left to the blue- print boy, who hangs them to dry on lines and sticks in much' the same manner as the first blueprint on earth was dried. Prints dried by this primitive method are wrinkled and present an untidy appearance in general even before being used; but we have learned to accept this condition as a matter of course where there is no ironing machine.
A WOODEN BLUEPRINT CLIP
The illustration shows a home-made blueprint clip which the writer has found to answer the requirements satisfactorily. It is made of wood and consists of a body having a large open slot in one end and a trigger hinged at right angles to this slot. The trigger must work freely in order that it may fall into place of its own weight. The length of the trigger must be so calculated that the outer end strikes the opposite side of the slot at a point slightly above the center line. A small nail or wire serves as a hinge for the trigger. A hole is made in the body, as at A, and a number of the clips, depending on requirements, are strung on a line. At least two clips must be used to hang one blueprint, but three or four should be used for the larger-sized sheets to make them hang smoothly. The hole should be made no larger than necessary, so that if the clip is pulled to an oblique position it causes a binding action. This feature is useful for the purpose of stretching the blueprints and making them hang smoothly. The clips in the corners of the blueprints shown are used in this manner. These clips require no manipulation except to slide them into place on the line, which can easily be done while holding the wet blueprint in the hands. Blueprints dried on these clips are as smooth as if ironed.
(19)
Knurling in the Small Shop
BY JOHN H. VAN DEVENTER
SYNOPSIS — This article describes the methods of marking and using knurls. Cut, rolled and fancy knurls are described, and methods are given for using them on all the machines found in the small shop.
Every machinist and almost every apprentice has in his tool box one or more knurls that he is quite sure beat anything any other man ever made. Also, very good knurls in a large assortment of patterns may be bought ready to mount in a holder and use. With this prolific source of supply it may be asked why the small- shop man should be interested in knowing how to make knurls. But a small-shop man must be posted on many things that the large-shop man does not need to know, for in the course of his varied and exciting existence
it
STeeffi perlnch
ISTeeth perlnci
ZOTeefh perlnch
Fine
Coarse wwvw\A Me FIG. 1.' ANGLES FOR CUTTING COARSE, MEDIUM AND FINE SPIRAL, KNURLS
FIG. 2. ANGLES FOR TEETH
FIG. 3. OBTAINING THE DEPTH OF KNURLED TEETH
he rubs up against circumstances that are quite outside of his snecial line. And also, a knowledge of how things are made does not interfere with knowing how to employ them.
Knurling is one branch of the process by which impres- sions are transferred from one material to another by rolling. It is in the same class as thread rolling and the making of index dials by the rolling; process. Knurling is applied to both flat and curved surfaces, and the tool itself may be either flat or curved. Where the work is flat, the knurl is circular; but when the work is circular, the knurl may be either circular or flat. An example of circular work and flat tool is the method of knurling work held in lathe centers by allow- ing a coarse file to "float" upon it.
I will pass up the ornamental knurls for the present and speak of the kind that will be found of greatest service in small shops — the straight and spiral patterns. These are originally produced by cutting what is known as a " master knurl." From this master, which is the same as the impression desired on the work, other knurls are produced by rolling and are used in the shop, the master being kept for reproducing purposes. Sometimes
this process is carried back and forth many times, until the offspring lose their family resemblance. The great- grandchild of a master knurl will not produce as good work as his grand-daddy, and for this reason the best knurling is procured directly from machine-cut knurls without the use of masters.
The knurl has been called a " putting-on tool." It increases the diameter of the work, because metal is forced up between the knurl teeth. Knurls and thread rolls are similar in their action, knurling being simply a case of rolling multiple threads. The stock diameter increases in knurling as it does in thread milling and in bqth cases may be figured roughly as equal to the depth of the tooth produced, this being the same* as saying that the knurl tooth goes down halfway into the stock and forces the stock halfway up into itself. The coarser the pitch of the teeth of the knurl the deeper
FIG. 4. VARYING THE DEPTH OF CUT GIVES SOME RANGE AS TO THE NUMBER OF TOOTH IMPRESSIONS
ABC
FIG. 5. PATTERNS OBTAINED WITH DIAMOND KNURLS BY VARYING THE DEPTH OF CUT
these teeth become. The result is that more pressure must be brought against the work in order to raise the impression. For straight and spiral knurls it is well not to have less than eight teeth per inch for the coarsest pitch.
In a spiral knurl the finer the pitch the less may be the angle made with the axis of the knurl. This is shown in Fig. 1, which gives pitch and angles for coarse, medium and fine spiral knurls. The greater this spiral angle becomes the less is the " bite " taken across the face of the kn*url, and it is for 'this reason that this angle is made greater on the coarse pitches. It also follows that a finer feed must be employed on coarse- pitch knurls than on fine-pitch ones, in order to get full tooth impressions.
The angle of the knurl tooth varies with the hardness of the material to be knurled. Various angles are illustrated in Fig. 2; they are suitable for brass, soft steel and tool steel. It also follows that the harder the material to be knurled the finer should be the pitch of the knurl, so that a sharp tooth angle and a fine pitch usually go together. This distinction, so far as hardness- is concerned, is an important one. (20)
KNURLING IN THE SMALL SHOP
Having the circular pitch of a spiral knurl and the number of teeth, the diameter is found by multiplying the circular pitch by the number of teeth. A simple way of obtaining the tooth depth is given in Fig. 3. XY and YG are laid out' at right angles, and points A and B are laid out on line XY at a distance apart corre- sponding to the circular pitch of the knurl. Through these points lines AC and BG are drawn representing the teeth and making an angle with the line YZ equal to the angle of the spiral knurl. The line CB is drawn perpendicular to the line AC, and the lines CF and BF are drawn at an angle A equal to one-half of 180 deg. minus the tooth angle as shown in Fig. 2. In other
(180 — 60) words, for tool steel the angle A will be -
2
60 deg. For brass the angle A will be 45 deg. and for soft steel 55 deg. The height of the triangle thus formed, represented by the line EF, will be the tooth
PIG. 6.
A SIMPLE ARRANGEMENT FOR MAKING A SPIRAL KNURL ON THE MILLER
depth. If this diagram is laid out on paper ten times full size, the depth may be read off in thousandths of an inch by means of a scale reading in hundredths.
These calculations apply to the diameter of the knurl itself, but a similar calculation is not often necessary for the diameter oi; stock, although in a case of coarse- pitch knurls an attempt must be made to get the correct stock diameter to avoid tooth impressions overlapping.
This diameter may be " found " more easily than it can be " calculated." The thing to do is to leave the stock a trifle large and reduce it until the tooth impressions come out with no overlapping. On fine-tooth knurls this is not necessary, for a little more or less pressure when the knurl gets to its depth will bring satisfactory results. If you have but one piece to knurl, it is better to use a fine knurl and not have to make experiments on the diameter; but if a large number of pieces are to, be knurled in the screw machine, the time spent in experimenting with one of them will not be of much importance.
Varying the depth of the cut gives a slight range as to number of tooth impressions, as shown in Fig. 4, and
also produces a variation in pattern in the case of diamond knurls, as may be seen in Fig. 5. Full-depth knurling produces the pattern at A. Fig. 5, while B and C are modifications corresponding to the depths at B and C, Fig. 4. If the object of knurling is to provide a grip for the hand, as upon a chuck body, knurling to part depth is advisable, since it gives sufficient rough- ness to enable the piece to be gripped without having the sharpness of full-depth knurling, which is likely to hurt the hand.
Straight-tooth knurls are easily cut on a lathe by holding the blank between centers and indexing on the
back gears. The tool is held horizontally in the tool post, and the carriage is moved back and forth by hand, thus planing the teeth. Spiral knurls are cut in a similar way on a universal miller having index centers. The divid- ing head is geared up for the correct lead of the spiral, and a single-point tool shaped to the angle of the knurled tooth is held in a fly-cutter holder such as is illustrated at A in Fig. 6. For ordinary work it is not necessary to rotate this fly- cutter; it is sufficient to hold it in a vertical position and plane the grooves by moving the 'table back and forth by hand, the dividing head with its gears taking care of the angular rotation of the work. When cut knurls are required in quantities, it is best to have a milling cutter. Surfaces formed with a radius may be knurled as shown at A and B in Fig. Y, the first being an example of convex straight and the second of spiral convex knurling. The radius of the rounding on a concave knurl, which is to produce a pattern on convex work
X
A
PIG. 7. PLAIN AND SPIRAL ROUND KNURLING
FIG. 8.
ARRANGEMENT FOR CUTTING CONCAVE AND 'CONVEX MASTER KNURLS
of this kind, must be slightly greater than the radius of the piece to be knurled, in order to prevent tearing of the work at the corners marked X in the illustration. A knurl for work of this sort is produced on a simple swivel tool-holding device, Fig. 8, the work being mounted on an index center and the single-point tool being swung on a radius across the face of the knurled blank. The point D shows the position of the pivot in producing a convex knurl, and E shows the position of the pivot when making a concave knurl. Both concave and
(21)
MAKING SMALL SHOPS PROFITABLE
convex knurls may be produced on the same device by shifting the position of the index center and of the tool with relation to the pivot pin.
Spiral convex knurling, such as shown at B, gives a very pleasing appearance, but requires more complicated arrangements for making the knurl. The universal miller is set up as for the straight- faced spiral knurl in Fig. 6, except that the tool is placed horizontally as at B. A templet is provided having a radius equal to that of the knurl, with the cross-feed, and this is followed while the longitud- inal feed produces the spiral. When a knurl is required for a pattern like
that in Fig. 9, in FIG- 9- HOLDER AND SPACING
COLLARS FOR "BUILT-UP"
which the diameter KNURL
of the various knuirled por- tions vary, it is a good scheme to make a " built-up " knurl with one roller for each por- tion and spacing collars be- tween. The separate knurls arc thus free to rotate at dif- ferent speeds to suit the di- ameter of the work. Even on work of one diameter, in which three or four spots are to be knurled in this way, a built-up knurl will often prove a good investment, as it enables the pattern to be changed and a broken tooth does not cause as much loss as it would in the case of a solid knurl. There is a vari- ety of ways to knurl in the hand screw machine and automatics. Sometimes the knurl is mounted on the cross- slide and is advanced directly in the work on the center line, as illustrated at A, Fig. 10, feeding in to the depth of the tooth and remaining a moment before being with- drawn. Another plan is to pass the knurl under the work, as at Ji, allowing it to rest a moment on the center line so that the tooth impressions become fully developed-.. Another plan makes use of the swinging arm, as at C, otherwise being similar in principle to A. Knurling
FIG. 10. GENERAL WAYS OF KNURLING ROUND STOCK ON SCREW MA- CHINE AND AUTO- MATICS
with a box tool having roller backrests is shown at B. The knurl E, Fig. 10, is swung in toward the work] by means of the eccentric F, and the plain rollers G running on each side of the knurled portion serve as backrests and balance the cut.
In connection with backresting, the location of the knurls and their number have an important effect on the strain produced in the work. The most common arrange- ment is illustrated at A, two knurls being held against one side of the work, resulting in a heavy unbalanced pressure. When one knurl is placed diametrically oppo- site the other on two opposite sides of the shaft, conditions are much better, although there still is a tendency for the rollers to ride up on the work in the direction of rotation. The scheme shown at C is the best of all, two rollers being mounted on one side of the shaft and one on the other, all tendency for rollers to ride up on the work being eliminated.
Ornamental knurling is an art not often practiced in the small shop. Artistic results can be obtained by knurls made as shown in Fig. 12, of which the result pictured at A is an example. The first step is to put in the ground lines, which consist of straight, fine-tooth knurling running across the piece, as at B. Punches are
FIG. 11. GOOD, BETTER AND BEST COMBINATIONS
made carrying one unit of the figure, such as shown at C and D. The work is then held upon the arbor of an index head, as at E, and the pattern is stamped by means of a hardened punch sliding in a fixed guide H. Doing this work by hand is a delicate job, requiring a great deal of skill in giving the blow required to make the impression. A better way is to rig up a light drop that insures the same weight of blow for each repetition of the figure. The fine-ground lines at B are not put in simply for ornamental effect, but to serve the purpose of gearing the knurl to the work. They are quite necessary on ornamental designs of this kind, which are not positively driven, but in which the knurl depends for its rotation and registry upon its contact with the work.
Another way to repeat a design of this sort is by rolling. A hob carrying a single impression is applied to the work by gears having teeth so figured that the hob is brought into contact with the surface of the work at a different place each revolution, until the entire surface has been covered with impressions. For example, if 40 impressions are desired on a circumference, these may be obtained by using gears having 40 and 39 teeth respectively, the former connected to the blank and the latter to the hob.
In making a knurl, use tool steel having a carbon content between 90 to 110 points. Make the hole for the pin on which the knurl is to rotate small in diameter
(22)
KNURLING IN THE SMALL SHOP
ON THE SPEED LATHE
IN THE SHAPER
IN THE VISE ON THE PRESS OR SLOTTEf? ON THE CHUCKING LATHE
PIG. 17. KNURLING DONE ON ALL THE TOOLS IN THE SMALL SHOP
(23)
MAKING SMALL SHOPS PROFITABLE
in order to reduce friction, and leave a collar on the side of the knurl for the same purpose. For a fancy knurl of complicated design it is best to use nonshrink- ing steel. Harden at a temperature corresponding to its carbon contents, as described on page 31, applying file cutters' paste to the knurl before heating. This is made up according to the following formula: Pulverized charred leather, 1 Ib. ; fine family flour, IVk Ib. ; table
FIG. 12.
ONE METHOD OF PRODUCING AN ORNAMENTAL MASTER KNURL
salt, 2 Ib. The charred leather should pass through a 45-mesh screen. The ingredients of this paste are mixed dry, after which water is added slowly and it is kneaded to prevent lumps from forming. It is used at the consistency of thin molasses, is applied to the knurl with a brush and allowed to dry before the piece is heated. After heating, the knurl is quenched in water and then drawn to a color between dark yellow and yellow brown.
Some 20 years ago Edward Board, of Philadelphia,, devised the triple adjustable knurl seen in Fig. 13. It combines the balance of forces described at C ' , Fig. 11, and has the good feature of being adjustable into the
FIG. 13.
ADJUSTABLE TRIPLE KNURL FOR HAND OR LATHE KNURLING
bargain. Mr. Board says that all small-shop owners are welcome to this idea, which is not patented, and which I can say from observation is a mighty good one for either hand or tool-post knurling.
One way to produce spiral knurling is shown in Fig. 14. In this case a straight knurl is inclined at an angle with the axis of the work and fed along by the tool carriage. This scheme is especially good for producing deep spiral knurling, as the teeth are cut to their full depth at the center of the knurl and there is no tendency
to break off the tooth corners. This advantage is offset by having to use a comparatively slow feed, since the band produced by a single rotation of the shaft is much narrower than would be produced by the knurl held parallel with the axis, as is clearly indicated at A, Fig. 14.
An adaptation of this principle for double spiral knurling is given in Fig. 15. In this case we have
Special Knurling with a Straight Knurl
fig. 16. ' Spring Holder For Light Knurling
Eccentric Work FIGS. 14, 15 AND 16. SPECIAL APPLICATIONS OF KNURLS
two straight knurls, both of them mounted and held at angles to the axis of the shaft and at right angles with respect to each other. The result is a diamond knurling, similar to that which would be made with a single spiral knurl held parallel to the axis. Deeper impressions of coarse pitches can be made with a knurl of this kind than with a spiral diamond knurl.
A scheme that has been used for knurling eccentrics is illustrated in Fig. 16. The tools are kept in contact with the work by means of the spring A, which must be sufficiently stiff to force the knurls into the work before the spring yields.
Sometimes knurled effects are produced not by knurling, but by stamping. An illustration of this is seen in Fig.
FIG. 17. KNURLED EFFECTS ARE PRODUCED BY STAMPING
17, which represents the roughening of one of a pair of plier handles by this simple means.
Although there is as a rule a machine best fitted for each kind of work to be done, this does not seem to hold true when it comes to knurling. The illustrations in Fig. 18 show how knurling may be accomplished in every machine usually found in the small shop and also by hand in the vise. If all work was subjected to such flexibility of handling, the small-shop man's trouble would be over I
(24)
Screw Threads in Small Shops
BY JOHN H. VAN DEVENTER
SYNOPSIS — Every shop has much to do with screw threads, especially in their broadest appli- cation as means for holding machine parts to- gether. Many shops lose money through not being "on to the curves" of the simple but sometimes aggravating machine elements. This article deals with various methods of screw cutting applicable to small shops.
When you buy a suit of clothes, you do not give a thought to the unseen thread that holds the pieces of cloth together. But let this unseen thread fail to do its duty in some important seam, and it becomes to you momentarily the most important thing in the world !
There is a close analogy between threads and threads, as applied in the textile and mechanical fields. Both of them hold things together, both have been given the same
PIG. 1.
CUTTING ONE SIDE OP THE THREAD SPACE IS BETTER THAN CUTTING BOTH
name; and take either away from its field of application and you put civilization back many centuries.
History does not give us a description of the man who first cut a screw thread, so we are at a loss to know whether this thread was cut to the United States stand- ard, the sharp V-standard, the Whitworth standard, the British Association standard, the French metric standard, the International standard, the Lowenherz standard, the acme standard, the Cadillac standard, the square stand- ard, the Briggs pipe standard, the British pipe standard, the hose standard, the British standard fine screw, the Society of Automobile Engineers standard, the American Society of Mechanical Engineers machine-screw standard, the old standard of machine screws, the gas-fixture standard or the Cycle Engineers standard.
Being a pioneer has its advantages, one of them being that you do not have such a conglomeration of established standards to worry about and choose from. To think of the brain energy that has followed the convolutions of all of these different standard screw threads makes one as dizzy as Mark Twain's " drop of whiskey running down a corkscrew." Picture to yourself the numerous conclaves of the wise men of all the nations necessary to establish such an unholy medley of- standards, the fuming ,and fussing and evaporation of brain vapor that were required to invent, establish and sort these 57 varieties! National societies have sat in discussion upon it, universities have deliberated upon it, corporations have investigated it, and in fact, taken all-in-all, this simple mechanical element has had almost as much public discussion as any of the " big " issues of the day.
The regrettable thing about it is that with all this thought, talk and action, while we have standards giving the dimensions, angles and proportions of screw threads, with a few exceptions we have not yet had laid down what
is more important for the shopman — the limits defining these standards. One of the notable exceptions to this is the A. S. M. E. standard for machine screws, which has been adopted by all tap and die makers.
While there are so many standards to choose from, the small-shop man need not be in a dilemma about which one to take. Outside of repair jobs, which call for special threads, nine-tenths of his work is or should be restricted to the II. S. standard, and the other one-tenth which will call for a finer pitch, should be divided between the A. S. M. E. standard for machine screws for diameters under % in. and the S. A. E. standard for the fine-pitch threads between % and 1 in. There is no excuse for making special taps in the small shop, and the policy of sticking to these established standards will save money.
Do not attempt to hog repair business by using a special thread standard of your own, for nothing makes the user of a machine more angry than to find that some screw that has been lost or broken is a special one and must be replaced at the factory. You may lose a cent or two of profit by not having the repair order come to you, but you are likely to lose the customer's business if you adopt such a small and mean policy. And by all means steer clear of the V-thread. It is not as strong as' the II. S. standard and is more easily damaged on account of its sharp edges. When the V-thread and the II. S. standard get together in a shop, trouble begins, especially when one tries to use a V-standard screw in connection with a II. S. standard nut. Nothing but main strength and the compressibility of metal save the day under such circumstances !
Before speaking of the accuracy and errors of screws, it is well to distinguish between the two main purposes for
PIG. 2. RIGGING UP TO CUT A "QUICK" LEAD IN THE LATHE
which they are used: One class must be very accurate indeed, this comprising the lead screws, dividing screws and the like, which may be classed as " precision " screws'. The broader application as fastenings, comprising bolts, studs, nuts, machine screws and the like, while they do not require the extreme precision of these former screws, must still be held to certain dimensions in order to reduce the shop owner's expense and the shop assembler's pro- fanity, when it comes to putting things together.
(25)
MAKING SMALL SHOPS PROFITABLE
In screw fastenings, errors of lead such as are ordi- narily found in commercial taps and dies are not import- ant, since the thickness of the tapped piece into which the screw is entered is ordinarily not greater than the diameter of the screw itself. There is small need to worry about slight errors of lead on this class of work, especially if the shop owner gives his taps and dies an accurate inspection after receiving them.
A great deal of tap wear and breakage can be eliminated from both small and large shops by the use of better judg- ment in the selection of tap-drill sizes. Size for size as compared with other tools the tap does a lot of work. The length of cutting edge in contact with the work in any tap is considerable. It is yanked through metal by main strength or driven through by an unfeeling machine, and in either case the cutting edges suffer accordingly, espe- cially if the tap drill is small. In most places where screw threads are used for fastening pieces together the maxi- mum strength of the thread is not required. It is merely a case of holding one piece of metal to another, and the strain which tends to separate them is not enough to stress the screw to anywhere near its safe limit.
Yet under these conditions you will find no distinction made in the shop as to the size of the tap drill used. In many such cases a drill is selected that is even smaller than the root diameter of the thread, which means that the tap must do the work of a reamer as well as its own. It has been shown that if the threads in a nut are made but 50 per cent, of the full depth of the standard thread, they are as strong as the bolt!
TABLE OP TAP-DRILL SIZES, U.S.S.
(For thread depths equal to 50, 75 and 90 per cent, of full thread)
Tap Drill Tap Drill Tap Drill for 50 per for 75 per for 90 per Cent. Depth Cent. Depth Cent. Depth i%4 No. lit Oie) % D* (%)
Diameter
%2 J*0%4)
2%4 3%4
as
5%4
«£
3%4
?%4
w
No. of Threads
% 20
$16 18
% 16
7/16 14
% 13
%'. '. '. 11
Hie 11
% 10 .
1%6 10 '
% 9
14ie 9
1 S
1 Vl6
W,»'. '.'.'.'.'.'.'.'.'.'.'. 7 H4 7
1%"'. '.'.'.'.'.'.'.'.'.'.'. 6 1% 6
ft:::::::::::: 8*
1% 5
2 4%
* Letter-size drill ; if not available, use size given in paren- thesis, t Wire-size drill ; if not available, use size given in parenthesis.
The relation between tap-drill size and the elbow grease required to drive a tap is not realized until you have pulled a a^-in. tap through 3 or 4 in. of steel. I had this experience during the early days of apprenticeship at a Middle Western tool works. The job was given to the newest apprentice, with the idea that while he and the shop helper were pulling their lungs out at opposite ends of a double-end tap wrench he would absorb the first prin- ciples of machine-tool building, which in those days was more sweat than science. Fortunately the pipe shop was not far removed, and more fortunately there was plenty of room all around the casting which was to be tapped, so that, before long, science came to the aid with two 14-ft. lengths of IV^-in. pipe that reduced the pvdl and increased the walk.
But even so it was a slow walk, for the tap had been preceded by a drill that was scarcely larger than the root diameter of the threads and it took close to a day and a half to finish what might have been accomplished in an hour or two at most with equally good results, had the hole been drilled somewhat larger. Nothing on earth could have stripped those threads, I am sure, even had they been half-threads only, for that steel was the toughest material that ever escaped from a steel-foundry scrap heap!
The table of tap-drill sizes given here will enable the small-shop man to use judgment and save his taps. In no
FIG. 3.
MILLING THREADS WITH A SINGLE CUTTER AND WITH MULTIPLE CUTTERS
case should he use a tap drill smaller than 90 per cent, of the depth of the thread, such as is given in the third column. For machine tapping, a 75 per cent, depth is ample; and in fact if the hole is made smaller, tap breakage will be a considerable item. For ordinary screw fastenings where no great strain or pressure is brought against the parts, 50 per cent, of depth will answer the purpose except in cast iron. The speed of tapping is largely influenced by the selection of the tap-drill size and increases much faster than the percentage of full thread depth decreases.
Hand tapping should be looked upon as a very expen- sive way to do the work; in fact, it should be regarded as similar to the crude method of ratcheting a hole instead of machine drilling it. Even when a close fit is desired, the holes should first be machine tapped with an undersized tap and then retapped to size by hand. Eetapping with a sizing tap is the only way in which a large number of tapped holes can be kept to a close standard of size, as has
(26)
SCREW THREADS IN SMALL SHOPS
been discovered by those who have had experience in shell work. This is a natural thing to expect, as the shop- man would scarcely think of using any other form tool but a tap for both roughing and finishing cuts, with the expectation of holding size. There is no reason why this cutting tool should be an exception to the rule, and shop- men are rapidly finding that it is not.
The only machine tapper available in small shops is quite likely to be the drilling machine. Even if this is not fitted with reversing gears, a tapping chuck can be obtained that is automatic in its action and that will start to back the tap as soon as the feed lever is raised. These tapping chucks are not only reliable, but are time savers, and no small shop can afford to be without one. When the work runs in large quantities of one or two tap sizes, it is time to consider a tapping machine. Some of these are very simple in construction, and in fact one of the most convenient I ever saw was a home-made affair in which a horizontal spindle was controlled by two fric- tion gears, the tap going into the work when the operator pushed the piece against it and backing out with a fast reverse motion when he started to pull. A contrivance of this kind will tap an al- most incredible number of holes without getting stiff in the joints, which is more than can be said for the average vise hand. Proba- bly 90 per cent, of the screws used in the small shops are die cut. Like all female threads, those in dies are infernally hard to measure. The best test of the die is the work that it does; and its offspring being all of the male gender, one can readily measure and inspect them.
All threads come originally from the King of Machines, the engine lathe. One of the best kinks in cutting threads on a lathe with a single tool is that attributed to Professor Sweet, in which the compound rest is swiveled 30 deg., so that instead of feeding directly into the work and cut- ting on both sides of the thread the tool has a one-sided cut, as shown in Fig. 1. This scheme prevents torn threads and is not as widely used as it should be.
SCREW CUTTING ON THE LATHE
While the lathe has the ability to develop a thread through its lead screw by means of a single-pointed tool, it is not by any means restricted to such high-grade but expensive kind of work. It will carry either a tap or a die and thus transform itself without protest into a tap- ping machine or a bolt cutter. And speaking of bolt cut- ters, some very pretty screw threads are produced on these machines, which are sometimes considered to be crude. Their work is not by any means restricted to threading rough bolts, however, and they can be applied for short feed screws such as are used in blacksmith drills and the
(2
FIG. 4. THREADING WITH A LEADER ON THE DRILL- ING MACHINE
like, where the exact lead need not be held to close limits. A bolt cutter will produce just as finely finished threads as a screw machine, for in both cases the quality pf "the work and the lead depend upon the die, the machine simply being the means of making things go around and important mainly for driving power.
When the small-shop man gets up to leads of l1/^ in. or over, he begins to have trouble with the feed works of his lathe. Such leads are not common on screw threads pure and simple, but are not infrequent on its close cousin, the worm, and on some multi-thread screws. In such cases change gears can be saved from breaking and the job may be made easier by rigging up as shown in Fig. 2, on the principle that there is always less strain involved in slowing down than in speeding up.
ACCURATE SCREWS ON THE THREAD MILLER
Since the advent of the thread miller, the lathe with its single-point tool is not the only machine which can pro- duce accurate screws. A positive lead is used in this milling process, the accuracy of the product, as far as lead is concerned, depending upon the accuracy of the miller lead screw, just as it does on the lead screw in lathe work. The thread miller has another advantage in being a semi- automatic machine and thus slicing off a large portion of the labor required to cut a screw. While a specialized machine of this type is possibly outside the range of most small shops, adaptations of the milling process are not. Some of these are shown in Fig. 3.
At A is an attachment rigged up on a plain miller of the knee and column type. The cutter is a plain grooved cutter and has no lead. The length of the cutter is equal to the length of the thread desired on the work, which is held in a fixture having a master screw of the same pitch as the cutter. One rotation of the work mills the entire length of thread and does it in about one-tenth the time that is required by any other method. This is a scheme that has been largely applied to milling internal threads in the base recesses of high-explosive shells where there is not room enough for a tap to clear, the recess at the bottom of the thread being just about equal to the width of one thread. This is shown at B in Fig. 3.
MILLING THREADS WITH A SINGLE CUTTER
It is not necessary to mill threads with a multiple- cutter, for they can be handled as shown at C, in which a cutter is used having the form of a single tooth space. The work is held and moved as in the previous case. This is the principle employed in thread milling, except that the cutter is moved instead of the work. A more accurate thread can be produced by a single cutter than by a mul- ' tiple cutter, owing to the changes in form and pitch which the latter undergoes in hardening. Any one of these three schemes may come in handy in a small shop when there is a quantity of work to be done at low cost and yet at a profit.
Even the vertical drilling machine may be made to cut a thread with positive lead and a single-pointed tool if it is rigged up as shown in Fig. 4. There are some jobs too large to be swung on a lathe, which may be handled this way to advantage, although to be sure it is a slow and clumsy way to do the work. Sometimes slow ways are the only ways, however, and this kink should be stored away in the small-shop man's mind for use on an occasion of that kind.
Measuring Screw Threads in the Small Shop
BY JOHN H. VAN DEVEXTER
SYNOPSIS — Measuring screw threads is a task that is undertaken with uncertainty in many shops. Sing and plug screw gages are commonly used, but do not always throw true light on the existing errors. This article tells how the small-shop man can measure threads with certainty, and also points out the sources of error to be looked for.
Casey was a good Irishman and a better mechanic, and was disgusted with the loss of time in his shop when it came to fitting screw threads. There were a good many studs to drive, and it was always a matter of sort and try to find those which would go in with the proper amount of pull. Some of them would fall in like a shot in a barrel and others would not even enter the hole. So Casey rigged up a block as shown in Fig. 1 in order that he
FIG. 1. THE OLD METHOD OF TRYING A SCREW IN A STANDARD HOLE STILL ANSWERS
FI.G 2. CRUDE AS IT IS, THE SCREW PLUG SEEMS TO HAVE A MONOPOLY ON THREADED HOLES
might establish a standard. He succeeded in having his screws made to fit the block, but found that tapmakers seemed to have a difference of opinion regarding the size of a half inch. " Begorry," said Casey, " what an argu- ment them fellows would have about the diameter of the earth if they've got such a difference of opinion on a half inch ! "
This variance in the sizes of taps exists for the simple reason that the learned bodies mentioned in the article on page 25, when establishing the various screw thread standards, did not complete their job and also establish a
set of maximum and minimum limits on them. But the matter 'of importance and interest is not what these gen- tlemen did not do but what the small-shop man must do in order to be sure that threads will fit the holes for which they are intended.
There are twelve errors which may creep into the thread of a nut and there are twelve similar errors which may creep into the threads of a screw, so all together we have twenty-four reasons why one will not fit the other. These, for the sake of clearness, are arranged in the accompany- ing table.
Making the outside and root diameter of a screw too small will not affect the fit unless these errors are exces-
FIG. 3. THE RIGHT PITCH, BUT THE WRONG THREAD ANGLE FOR A PERFECT FIT
FIG. 4. THE SCREW TOO SMALL, BUT BINDING IN THE LEAD, SO THE CONTACT IS LIMITED
sive. Conversely, making the root and outside diameters of a nut too -large often helps things instead of harming them. When the reverse is true, however, and the outside diameter of a screw is larger than the root diameter of the nut, there is trouble. This is usually what is encoun- tered when one tries to screw a V-thread into a TJ. S. S. nut The way to overcome this difficulty is to keep the V standard out of the shop. Sometimes the wrong thread angle on either screw or nut makes a defective fit which cannot be noticed because the pitch happens to be right. A case of this kind is shown in Fig. 3, where there is
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MEASURING SCREW THREADS IN THE SMALL SHOP
contact at the extreme corners of the threads and conse- quently no shape but a very poor fit. Another poor fit is shown in Fig. 4, in which the lead is stretched, apparently making a tight driving fit, but in reality having contact only on the surfaces of two or three threads.
Sometimes the pitch of both nut and screw may be right, the lead right, the angle right, the outside and root
ERRORS IN THREADED WORK
Diameter (outside) .................. } £00 J^ff,
Diameter (pitch) .................... ,(T,oo j^ge
Diameter (root) ..................... ) ?oo Lmafl
Angle of thread ..................... {££ Jgg
Pitch of threads
Lead — Not uniform Burrs and bruises
diameters right, but everything all wrong nevertheless. This is because of the vital dimension, which cannot be seen and which is hard to measure, which is known as the
FIG. 5. SOME VARIATIONS IN DIAMETER ARE HARMLESS
FIG. 6. THE PITCH RIGHT. THE LEAD RIGHT, THE ANGLE RIGHT — BUT ALL WRONG, NEVERTHELESS
FIG. 7. TESTING THE LEAD WITH A SCREW PITCH GAGE
pitch diameter. A case of this kind is illustrated in Fig. 6 and would give a very shaky fit, while an error of the opposite kind in which the threads of the screw were too thick would make it impossible to enter the screw. For- tunately for most small-shop purposes, it is safe to assume that the angles of threads on purchased taps and dies are correct. Also for this class of work it is quite possible to test the lead of a screw by means of a gage such as shown in Fig. 7. These gages run from 2 to 4 in. in length, depending on the fineness of the pitch, and a little experience will make the shop man an expert in their use.
Limit thread gages for testing pitch diameters form a means of inspection that is absolutely decisive. These are used on precision work, but an individual gage is required for each diameter and pitch, which usually limits their application to shops in which a large quantity of pieces
having a limited number of thread sizes are handled. For average small-shop requirements, which will not call for measuring every screw used, three methods of measuring pitch diameter are available — the thread micrometer, the ball-point micrometers and the two- and three-wire .sys- tems. The latter can be used with an ordinary pair of mikes such as will be found in every small shop, and will
FIG. 8.
LIMIT THREAD GAGES FOR TESTING PITCH DIAMETER
FIG. 9. MEASURING THREADS BY THE TWO- AND THREE-WIRE SYSTEMS
FIG. 10. TESTING A TAP FOR WARP BETWEEN LATHE CENTERS
give as accurate results as any method of measurement although a little slower than the special micrometers made for this purpose. The method of using the two- and three- wire systems is indicated in Fig. 9. Wires are taken of proper size and measurement made across their outside diameters when laid in opposite thread spaces. The micrometer readings are compared with a table which gives the reading in terms of pitch diameter. Tables for this purpose for all of the standard threads can be found in the " American Machinist Handbook," pages 30 to 40.
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MAKING SMALL SHOPS PROFITABLE
While the thread angles on taps may be assumed to be correct, there are other things which it would be well to check up as soon as the taps come into the shop. A set of inspections for checking up taps are illustrated in Figs. 10 to 13. The first illustration shows a tap placed between lathe centers and being tested for warp and eccen- tricity due to distortion in hardening. Fig. 11 shows the
PIG. 11. COMPARING THE LEAD OF A TAP WITH THAT OF THE LATHE LEAD SCREW
FIG. 12. MEASURING THE OUTSIDE DIAMETER OF THE TAP TO INSURE A FULL ROOT DIAMETER
means of comparing the lead of a tap with that of the lathe lead screw, which will indicate an error in the tap provided the lathe screw itself is accurate. An indicator is held in the tool post with its needle against one side of the tap face, the lead screw is engaged, the operator turns the belt by hand and eases off on the indicator needle from space to space, observing any fluctuation as the needle comes to rest on successive flutes. If the tap lead is right and the lathe screw lead is right, there should be no variation on the indicator.
The outside diameter of the tap must be large enough to insure a full root diameter of the tapped hole. This is measured, with a pair of " mikes " as shown in Fig. 12. The final test is that of the pitch diameter, which is made as shown in Fig. 13, and which has been explained in the description of the three-wire system. If a tap passes these
four inspections satisfactorily, it is a pretty good tool as far as accuracy is concerned. To insure that the bolts, screws and studs that are purchased outside will fit prop- erly into threads made 'with such a tap, it is advisable to inspect one or two of such studs, bolts or screws in every one hundred by means of running them into a block such as shown in Fig. 1. This, called selective inspection, will call attention to batches of screws which are running over or under size, in which case a further inspection of each screw in that batch may be made if desired before return- ing them to the maker. It is advisable for the small-shop man to protect himself in buying such screws by submit- ting a similar gage at the time that he gives the order.
Dies are best inspected by examining the work that comes from them. Do not, however, make the mistake as did one small-shop man of testing an adjustable die
FIG.
MEASURING THE PITCH DIAMETER WITH " MIKES " AND WIRES
with stock that was larger than that intended for the chasers that were used. The chasers were supposed to cut twelve threads to the inch, but after the work came out of the die he could find but thirty-five threads in 3 in. One of them had disappeared mysteriously, and he is still hunt- ing for it !
Lifting the Shaper Chuck
BY G. A. REMY
The vise, or chuck, on large shapers is heavy and, owing to its form, difficult to lift and place in position on the shaper table. Recently I saw three men put a large chuck in position without trouble, in the following manner :
Before the chuck was removed from the shaper, a piece of iron pipe was clamped between the vise jaws, the ends of the pipe protruding from the chuck far enough to furnish a grip. A man on each side lifted the chuck and, thanks to the pipe, easily held it in position over the table while a third man inserted the binding bolts and wiped away any chips that had fallen from the chuck to the table.
This is a simple method, but one not generally prac- ticed. Besides avoiding the strain on the men in lifting, the machine is saved many hard knocks, which generally result when the men lifting the chuck have a poor grip. This idea is not original with me. I have seen it used by shaper hands.
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Hardening and Softening Steels in the Small
Shop
BY JOHN H. VAN DEVENTER
SYNOPSIS— This article throws light on some right and some wrong ways to harden and anneal carbon and high-speed steels. The use of lead balhs, cyanide of potassium and various quenching com- positions is treated in detail.
To take his diploma as an all-round small-shop machin- ist, a man must, in addition to many other requirements, be a fair blacksmith and a first-class tool hardener. The average small-shop owner cannot afford such a luxury as a tool specialist and may perhaps consider himself lucky that he cannot. The idea of specialization has been carried too far. If specialization were the real and ulti- mate object of man, we should be built differently. Some of us would have nothing but noses — we should do the smelling for the community; others would be exclusive specialists at seeing, and others at hearing. As it is, we are all constructed very much alike and evidently intended by nature to do many things well, although the teachings of the " superspecialists " would make us believe to the contrary.
Judging by the number of inquiries received by the American Machinist for information, the hardening and annealing of steels is a matter that is worth presenting to small-shop readers. Like a good many other subjects, different parts of it have been presented from time to time, dispersed over a number of volumes and a number of issues — each one bearing its share of information. In one or two articles on this subject I will try to gather together the most important things to be known and done in connection with hardening and annealing, especially from the viewpoint of practicability for use in the small shop.
METHODS OF HEATING FOR HARDENING AND TEMPERING
The various ways of heating steels group themselves into three distinct divisions : First, in the open fire, in which the piece to be heated is exposed directly to the fuel. This scheme, the oldest, the best known and the commonest, is the one followed in ninety-nine shops out of a hundred. The blacksmith forge as a hardening and tem- pering appliance is as well known in the large shop as in the small one, and provided care is taken to use fuel free from sulphur and phosphorus and to build the fire deep enough so that the heated metal is not exposed to the direct blast, good results can be obtained. In using the open fire the degree of heat must be gaged by color, which is a disadvantage of this method of heating. While it may give best results some of the time and good results most of the time, it will not give best results all of the time, such as are assured when the degree of heat can be accurately measured and controlled.
The second classification of heating devices may be described as closed retorts or furnaces, in which the piece is protected not only from drafts, but also from attacks by the gases and chemical elements in the fuel. The size of such an outfit may vary from a muffle capable of being juggled about in one hand to a gigantic furnace. When
a furnace of this type is fired by oil or gas and is provided with a pyrometer, such as described on page 38, the heat may be closely regulated. I must not forget to mention in this class the electrically heated furnace, which is no doubt the most accurately controlled of any and which is largely used by makers of high-grade small tools as a means of heating their product.
HEATING THE WORK IN A HOT BATH
The third class of heating appliances may be indexed under the name " Bath," although quite different from the Saturday night bath of the small-shop man. It may consist of a pot of melted lead, of melted salt, of potas- sium cyanide, of sand or of heavy oil. These are of course hot baths, as distinguished from the quenching or cooling baths, which will be mentioned later. The advan- tages of a bath of this kind are easily obtained in the small shop by placing upon the forge a crucible or an iron ket- tle containing the bath material. A better way to heat it and one that allows for regulation is by means of a gas or crude-oil burner.
The reason for uniformity of temperature in harden- ing steels may not be fully understood; and when not, it is difficult for one to realize the importance of main- taining a uniform temperature. In its action, when heated, steel somewhat resembles water. Just as heated water reaches a point where it boils and changes into steam, steel heated sufficiently reaches a point where its particles are changed in their nature and relation. On being cooled to a temperature a little lower than the first the particles will change back again.
These temperatures are called the " critical points " of the steel and vary with different percentages of carbon. The proper hardening temperature is from 30 to 50 deg. above the first critical point. The ideal temperature would be exactly at this point, but allowance must be thus made for cooling in the interval of time before quenching. A table showing these temperatures is given for various per- centages of carbon, and it will be noticed that the higher the carbon of the steel the lower this critical temperature becomes.
Steel has a peculiar property of losing its power of attracting a magnet when the critical point is reached, and this fact is taken advantage of by some small-shop owners who do not have pyrometers. A magnetic compass is applied to the piece of heated steel; and when the needle ceases to be attracted by it, the shop man knows that the critical point has been reached.
HARDENING AND ANNEALING TEMPERATURES FOR CARBON STEELS
Per cent. Carbon 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 to 1.5
" Points "
10
20
30
40
50
• 60
70
80 to 150
Deg. F. 1,616 1.'562 1.535 1.508 1,492 1,481 1.476 1.472
The nearer to the critical point that the small-shop man is able to quench a piece of steel, the finer will be its grain. Its hardness and toughness will also reach a
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MAKING SMALL SHOPS PROFITABLE
maximum under these conditions. Over and under this point the grains become gradually coarser, and the hard- ness decreases.
One thing to remember in heating steels for harden- ing is to keep the temperature " going up " until the crit- ical point is reached. In other words, it will not do to go above this point and let the temperature drop before quenching. Apparently it is necessary to keep the tem- perature moving in one direction, in order not to impede traffic among the busy molecules of the heated bar. While this is true, it is equally true that fast heating must be avoided. A piece of steel is often heated so quickly that the outside only is in its proper critical condition.
Every mechanic who has had anything to do with the hardening of tools knows how necessary it is to take a cut from the surface of the bar that is to be hardened. The reason is that in the process of making the steel its outer surface has become decarbonized. This change makes it low-carbon steel, which will of course not harden. It is necessary to remove from %e to % in. of diameter on bars ranging from i/2 to 4 in.
This same decarbonization occurs if the steel is placed in the forge in such a way that unburned oxygen from the blast can get at it. The carbon is oxidized, or burned out, converting the outside of the steel into low-carbon steel. The way to avoid this catastrophe is to use a deep fire. Lack of this precaution is the cause of much spoiled work, not only because of decarbonization of the outer surface of the metal, but because the cold blast strik- ing the hot steel acts like boiling hot water poured into an ice-cold glass tumbler. The contraction sets up stresses that result in cracks when the piece is quenched. The next time you harden a milling cutter and have some 'of the teeth crack off, keep this suggestion in mind.
PREVENTING DECABBONIZATION OF TAPS AND REAMERS
It is especially important to prevent decarbonization in such tools as taps and form cutters, which must keep their shape after hardening and which cannot be ground away on the profile. For this reason it is well to put taps, reamers and the like into pieces of pipe in heating them. The pipe need be closed on one end only, as the air will not circulate readily unless there is an opening at both ends for a " draft," so to speak.
Even if used in connection with a blacksmiths' forge the lead bath has an advantage for heating tools of com- plicated shapes, since it is easier to heat them uniformly and they are submerged and away from the air. You must remember, however, that unless the metal is stirred, the temperature of such a bath is not uniform. And always remember to use powdered charcoal as a covering for the top of the lead pot. Some may ask why it is necessary to repeat such a simple precaution, but a prominent firm making shrapnel incurred much expense for wasted lead until someone suggested the use of charcoal. A lead bath may be used at temperatures between 620 and 1,150 deg. F. Beyond this there will be much waste by evap- oration, i
To secure proper hardness, the cooling or quenching of steel is as important as its heating. Quenching baths vary in nature, there being a large mimber of ways to cool a piece of steel in contrast to the comparatively few ways of heating it.
Plain water, brine and oil are the three most common quenching materials. Of these three the brine will give
the most hardness, and plain water and oil come next. The colder that any of these baths is when the piece is put into it the harder will be the steel; but this does not mean that it is a good plan to dip the heated steel into a tank of ice water, for the shock would be so great that the bar would probably fly to pieces. In fact, the quench- ing bath must be sometimes heated a bit to take off the edge of the shock.
Brine solutions will work uniformly, or give the same degree of hardness, until they reach a temperature of 150 deg. F., above which their grip relaxes and the metals quenched in them become softer. Plain water holds its grip up to a temperature of approximately 100 deg. F. ; but oil baths, which are used to secure a slower rate of cooling, may be used up to 500 deg. or more. A compro- mise is sometimes effected by using a bath consisting of an inch or two of oil floating on the surface of water. As the hot steel passes through the oil, the shock is not as severe as if it were to be thrust directly into the water; and in addition, oil adheres to the tool and keeps the water from direct contact with the metal.
The old idea that mercury will harden steel more than any other quenching material has been exploded. A bath consisting of melted cyanide of potassium is useful for heating fine engraved dies and other articles that are required to come out free from scale. One must be care- ful to provide a hood or exhaust system to get rid of the deadly fumes coming from the cyanide pot.
EASING OFF THE INTERNAL STRESSES
Work quenched from a high temperature and not after- ward tempered will, if complex in shape, contain many internal stresses, which may later cause it to break. They may be eased off by slight heating without materially less- ening the hardness of the piece. One way to do this is to hold the piece over a fire and test it as Mrs. Small-Shop Man tests her hot flatiron — with a moistened finger. Another way is to dip the piece in boiling water after it has first been quenched in a cold bath. Such steps are not necessary with articles which are afterward tempered and in which the strains are thus reduced.
In annealing steels the operation is similar to harden- ing, as far as heating is concerned. The critical tempera- tures given in the table are the proper ones for annealing as well as hardening. From this point on there is a differ- ence, for annealing consists in cooling as slowly as possible. The slower the cooling the softer will be the steel.
Annealing may be done in the open air, in furnaces, in hot ashes or lime, in powdered charcoal, in burnt bone, in charred leather and in water. There is surely some range of choice for the small-shop man when it comes to doing this work. Open-air annealing will do as a crude measure in cases where it is desired to take the internal stresses out of a piece. Care must be taken in using this method that the piece is not exposed to drafts or placed on some cold substance that will chill it. Furnace annealing is much better and consists in heating the piece in a furnace to the critical temperature . and then allowing the work and the furnace to cool together.
When lime or ashes are used as materials to keep air away from the steel and retain the heat, they should be first heated to make sure that they are dry. Powdered charcoal is used for high-grade annealing, the piece being packed in this substance in an iron box and both the work and the box raised to the critical temperature and
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HARDENING AND SOFTENING STEELS IN THE SMALL SHOP
PIG. 1. THE HOLE TO BE MADE
then allowed to cool slowly. Machinery steel may be annealed in spent ground-bone that has been used in casehardening ; but tool steel must never be annealed in this way, as it will be injured by the phosphorus contained in the bone. Charred leather is the best annealing material for high-carbon steel, because it prevents decarbonizing taking place.
Water annealing consists in heating the piece, allowing it to cool in air until it loses its red heat and becomes black and then immediately quenching it in water. This plan works well for very low-carbon steel; but for high-carbon steel what is known as the " double annealing treat- ment " must be given, provided results are wanted quickly, as is usually the case with water or oil-bath annealing. The process consists of quenching the steel in water or oil, as in hardening, and then reheating it to just below the critical point and again quenching it in oil. This process retains in the steel a fine-grain structure combined with softness. Large pieces of steel should be rough-turned before anneal- ing. It will not be necessary to say anything about color -tempering, this being a subject familiar to all. In drawing temper, however, the color is not the only gage that can be used. One of the best is a thermometer in a bath of heavy oil having a flash point between 500 and 600 deg., which will take care of all the tempers up to that corresponding to dark blue. The steel is first preheated slowly in a fire or furnace, as it might crack if plunged immediately into the hot oil. '.;:,
In hardening high-speed steel the main requirement is to get the cutting edge hot enough. The air blast for cooling is going out of fashion and an oil bath is taking its place, which will be good news to the small shop that has no air compressor. Lathe and planer tools are usually left in their quenched condition, for use, not being tem- pered or drawn. More complicated and expensive high- speed steel cutters are somewhat insured against break- age by drawing the temper slightly. Milling cutters are drawn to 400 deg. F., drills and reamers to 450 deg. and taps and dies are let down a little farther, not, however, reaching 500 deg.
Boring Pump Chambers in the Drilling Machine
BY A. N. PATTERSON
In the illustration, Fig. 1, is shown a pump-chamber pocket that was bored in a drill press. The top flange was faced, drilled and tapped before the boring was done. This was permissible, as the pockets had no relation one to the other, and the distances between centers of the cham- bers did not have to be absolutely accurate.
In Fig. 2 is shown the arrangement of tools for all operations. A is a plate to hold the. guide bushing B; this plate was secured to the :top flange by capscrews in the tapped holes. The method of operation is as follows : The boring bar in the spindle of the drill press is raised
clear of the work, the guide bushing B is slipped over the bar and the cutter inserted and secured. The bar is then lowered to the work, the bushing being pushed down in the plate, and the boring commenced.
A roughing and finishing cutter was used for each diameter to be bored. The dimensions of the bar and bushing were such that the bushing would enter the plate before the cutting commenced, so that the bar, was always guided when boring.
The tool used for chamfering the bottom of the hole is
FIG. 2. ARRANGEMENT OP TOOLS
FIG. 3. THE CHAMFER- ING TOOL
shown in Fig. 3. In doing this operation the bushing was raised clear of the plate and the boring bar and tool inserted eccentrically in the hole, to permit it to enter. The bushing was then forced into the plate, centering the bar, and by feeding upward the hole was chamfered.
A Handy Driver for Removing Shell Sockets
BY JOHN DUNN
The accompanying sketch shows a very handy driver for removing the brass socket from an 18-lb. shrapnel shell in order to correct the weight or put on a new socket.
The shell is first heated to break the solder joint between the brass socket and the tube. The plug is then screwed
Taper Pin (<....
SHELL-SOCKET REMOVER
in. Tightening the nut on top expands the plug; then by the use of a large wrench the socket may be backed out. This driver will not harm the socket, which may be put back in the ordinary way, and it makes an other- wise nasty job very easy.
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Carbonizing Small-Shop Steels
BY JOHN H. VAN DEVENTER
SYNOPSIS — Carbonizing is the first step in casehardening. Unless this part of the work is done with a knowledge of the principles involved, the final result will be uncertain. This article gives an explanation of the action of carbonizing processes as applied to both low- and high-carbon steels.
Out in the woods of North Carolina, ten miles from the nearest populated point, a gang of men were converting pine trees into rough lumber. For this purpose they used axes and a 'portable sawmill outfit run by a side-crank engine such as is commonly found in these migrating lumber camps. One day the boiler, which was rather inclined to bad attacks or spasms, delivered an unusually large gob of water through its discharge pipe to the long-suffering engine cylinder just at the time that the saw was biting its way through a pugnacious pine knot. The combination of circumstances was too much for the crosshead pin of the engine.
" I don't see what made the darn thing break," said the lanky North Carolinian who acted not only as boss of the outfit, but also as master mechanic. Indeed the fracture, to one who was not experienced in such matters, would appear to be a good one. Still, it was evident that something must have been wrong with the pin, for by all expectations the cylinder head should have gone before this part of the apparatus gave away.
To get at the real reason for this mishap, which meant the loss of many dollars and a shutdown of many days to this lumber camp, let us go back to the factory in which this crosshead pin was made and see how the work was done. If the lanky lumber-camp boss could go along with us and also see what caused the accident, I am sure that he would be more particular in the future in buying an engine and possibly willing to pay enough to avoid the junk that is frequently offered.
In the shop that built this engine the aim was not so much to give service as it was, to put it crudely, to find suckers. The idea was to produce an engine at the lowest possible cost, sell it at a price that would be an inducement much greater than quality and not worry too much about what happened to it after it was in use. One of the safeguards of this policy was the knowledge of many ways by which a skillful correspondent can make defects of construction appear as errors in operation.
To make the descriptive matter as imposing as possible, such items as charcoal-iron castings, hammered babbitt bearings and casehardened pins were described at length, although as a matter of actual fact the nearest that any charcoal got to the iron was in the fire used in drying the skin of the mold, and the only hammering that the bearings received was that due to the pounding of the rod after the engine was in service. As for the case- hardened pins, the blacksmith took them under his wing after they were fully machined, heated them up in his forge, sprinkled a little cyanide of potassium over their surfaces, turned them around in the fire once or twice, to get the same effect as is obtained by basting chickens.' and then plunged them into a cold brine solution. This
procedure did make the outer -skins of these pins very hard, but it left the inner core extremely coarse-grained and weak. The pin could not be touched with a file and might appear to be a very long-wearing product, but was brittle and weak. If it had really been wise on the subject of carbonizing and casehardening, this firm could have avoided this feature and also reduced the cost of carbonizing the crosshead pin — getting a high-grade result for less money.
Casehardening divides itself into two parts — carbon- izing and quenching. A great many people think that the quenching must be done at the same heat as that at which the piece is carbonized. This idea is entirely wrong, and these two processes can be regarded as separate operations; in fact, in this article I will stick to the
Fig.!. Cast-Iron Carburizing Box
„ i
>
Fig Z. Minimum Clearance of Work in Carburizing Box
_\\? V V '•!' 'l'^
~: ®iOO
£»• fj
Illustrating Unequal Carbur'zing
Wires forTming Carburizing Heats
FIGS. 1 TO 4. CARBONIZING BOXES AND DETAILS ILLUSTRATING THEIR USE
carbonizing part of it as closely as possible and save the quenching for another time.
There are four different reasons for casehardening, and they must be considered in connection with the way of doing it. The first is to secure a hard surface — maximum hardness to resist wear without shock. Again, a piece may be casehardened for the purpose of securing stiffness, thus reducing the- likelihood of the stretching of light sections while at the same time allowing the use of cheap machinery-steel stock. A third purpose is to secure colors on certain classes of work. The fourth, which is possibly the least understood in most shops, is that of securing a hard cutting edge, not only on low-carbon steels, but also on tool steels.
These different purposes are secured by the proper selection of the carbonizing material in which the articles are packed and of the bath in which they are quenched.
The general practice of carbonizing is as follows : The articles are placed in cast-iron boxes surrounded by materials that will give up carbon when heated. These boxes and their contents are next heated through, beyond the critical point of the steel involved (see page 31) and are allowed to soak at this temperature for a length
(34)
CARBONIZING SMALL-SHOP STEELS
of time depending on the depth of case wished. A con- venient box for this purpose is shown in Fig. 1.
There are certain precautions to be taken in packing a box of this kind. In the tug^of-war to absorb whatever free carbon is released by the heated carbonizing material, cast iron has a much stronger pull than has steel. As a result, if the pieces are placed too near the cast-iron walls of the containing box, these walls will get the benefit of the carbon to the detriment of the pieces. Fig. 2 shows a cross-section through a casehardening box and gives the minimum clearances for the articles with rela- tion to each other and to the walls and bottom of the box.
The casehardening box must not be too large, especially for light work that is run on a short heat. The reason for this is shown in the diagram in Fig. 3. When a box of this kind is put into a furnace, it heats from the outside toward the center, taking from one-half hour to an hour and a half to heat through uniformly, depending upon the liveliness of the fire. If the contents of such a box are dumped after a short heat, the pieces on the outside rows will have been at the carbonizing heat much larger than those nearer the center of the box, the result being a much greater gain in carbon in these outer pieces, as illustrated by the sectional shading in Fig. 3.
The temperature to be used for carbonizing depends on the amount of carbon already in the steel to be treated. This temperature must be above the critical point of the steel; and if you know its carbon contents, you can obtain this point from the table on page 31. Low-carbon machinery steel containing from 15 to 20 points carbon is commonly used for this purpose, and such steels must be heated to between 1,650 and 1,750 deg. F. The more carbon that there is in the steel to start with the slower it will be in taking on additional carbon and the lower is the temperature required. In ordinary casehardening, the outer surface of steel has its carbon increased from 15 or 20 points to 80 or 85 points. Tool steels may be carbonized as high as 250 points, but this amount is a maximum and is seldom, if ever, required.
The materials used for carbonizing are many. Among the most common are wood and bone charcoal, ground or crushed bone, charred leather, horns and hoofs. There
Cyanide of.. Cham* Leather *>+<•"«"» ' F'9 •
PIGS. 5 TO 9. LOCAL CARBONIZING BY THE USE OF VARIOUS METHODS
are also combined preparations, one of the best of which is a mixture of barium carbonite, 40 per cent., and charcoal, 60 per cent. This mixture gives a rate of pene- tration which is from 10 to 20 per cent, faster than that of charcoal, bone or leather. Fig. 10 shows the penetration of this mixture on ordinary low-carbon machinery-steel stock over a range of 2 to 12 hr.
Each of these different packing materials has a different effect upon the work in which it is heated. Charcoal by itself will give a rather light case. Mixed with raw bone it will carbonize more rapidly, and still more so if mixed with burnt bone. Raw bone and burnt bone, as may be inferred, are both quicker carbonizers than charcoal, but raw bone must never be used where the breakage of
0.050* ZHours
FIG. 10. ORDINARY CASE PENETRATION IN LOW-CARBON STEEL FOR VARIOUS HEATS
hardened edges is to be avoided, as it contains phosphorus and tends to make the piece brittle. Charred leather mixed with charcoal is a still faster material, and horns and hoofs exceed even this in speed ; but these two com- pounds are restricted by their cost to use with high-grade articles, usually of tool or high-carbon steel, that are to be hardened locally — that is, " pack-hardened." Cyanide of potassium and prussiate of potash are also included in the list of carbonizing materials; but outside of carbon- izing by dipping into melted baths of these materials, which I will describe later, their use is largely confined to local hardening of small surfaces, such as holes in dies and the like.
One of the advantages of hardening by carbonizing is the fact that you can arrange to leave part of the work soft and thus retain the toughness and strength of the original material. Figs. 5 and 9 show ways of doing this. The inside of the cup in Fig. 5 is locally hardened, as illustrated in Fig. 6, " spent " or used bone being packed around the surfaces that are to be left soft, while cyanide of potassium is put around those which are desired hard. The threads of the nut in Fig. 7 are kept soft by carbon- izing the nut while upon a stud. The profile gage, Fig. 8, is made of high-carbon steel and is hardened on the inside by packing with charred leather, but kept soft on the outside by surrounding it with fireclay. The rivet stud shown in Fig. 9 is carbonized while of its full diameter and then turned down to the size of the rivet end, thus cutting away the carbonized surface. Pieces of this kind are of course not quenched and hardened in the carbonizing heat, but are left in the box to cool, just as in box annealing, being reheated and quenched as a second operation. In fact, this is a good scheme to use for the majority of carbonizing work of small and moderate size. Sometimes it is wished to harden a thin piece of sheet steel halfway through, retaining the soft portion as a backing for strength. Material is on the market with which one side of the steel can be treated ; or copper-plating one side of it will answer the same pur- pose and prevent that side becoming carbonized.
(35)
Casehardening Small -Shop Steels
BY JOHN H. VAN DEVENTER
SYNOPSIS — This article deals with the subject of quenching case-carbonized articles and with the heat treatment of such pieces to secure maximum toughness. Pack-hardening is discussed and also the casehardening of alloy steels and cast iron. A combination quenching tank for hardening and coloring is illustrated.
All blacksmiths are by nature and training more or less experimenters, and very few have not some " secret " formula for accomplishing wonderful results in harden- ing. Cast-iron hardening has received a good part of their attention in this respect with varying degrees of success. While it has been an easy matter to make cast iron extremely hard on the surface — in fact, as hard as the hardest tool steel — no one has as yet found a way to add the element of strength to this hardness without which its use is limited to gages, templets and other things that do not require much strength.
Some amusing results often accompany such experi- ments. One blacksmith of my acquaintance, who had obtained very fair results with cast-iron hardening, was always searching for some chemical or compound to add to the quenching bath to make this " grip " the metal more forcibly. This " grip " is a noticeable thing in harden- ing cast iron; not only can you feel it on the end of the tongs, but when certain solutions are used, it becomes so forcible as to make itself heard — making one think that a miniature torpedo was exploding beneath the surface of the water. I was passing through his black- smith shop one day when a new mixture was being tried out. As soon as the blacksmith plunged the red- hot casting into the barrel containing this mixture, there was a violent explosion in which blacksmith, barrel, quenching mixture and casting were indiscriminately mixed. The experimenter picked himself up, felt of the various parts of his anatomy to see what was miss- ing and, finding himself intact, exclaimed regretfully: " Say, what a fine mixture that would be if you could only get a barrel strong enough to hold it! " I do not know what caused this explosion, but having seen it, can be sure that it happened and also that it put an end to the experimenting of this particular blacksmith, who afterward stuck to the tried and tested formulas. Prob- ably the heat of the casting was all that was needed to set up some powerful chemical reaction between the ele- ments in the bath.
An old formula that has done good service in the mat- ter of surface-hardening cast iron is as follows: To 20 gal. of water add 1 pint of oil of vitriol, 2 pecks of salt, 4 Ib. of alum, % Ib. yellow prussiate of potash, % Ib- cyanide of potash and 1 Ib. saltpeter. This bath can be kept in a covered wooden barrel. The casting is heated cherry-red and then plunged into this bath, which hardens its surface. Sometimes it is necessary to repeat this performance two or three times to get the surface sufficiently hard.
The quenching tank is an important feature of appara- tus in casehardening — possibly more so than in ordinary tempering. One reason for this is because of the large quantities of pieces usually dumped into the tank at a time. One cannot take time to separate the articles themselves from the casehardening mixture, and the whole content of the box is dropped into the bath in short order, as exposure to air of the heated work is fatal to results. Unless it is split up, it is likely to go to the bottom as a solid mass, in which case very few of the pieces are properly hardened. A combination cool- ing tank is shown in Fig. 1. Water inlet and outlet pipes are shown and also a drain plug that enables the
Comprfsseef-4/r Spray--
(under Mre Tray) — — ~
FIG. 1. COMBINATION COOLING TANK FOR CASEHARDENING
tank to be emptied when it is desired to clean out the spent carbonizing material from the bottom. A wire- bottomed tray, framed with angle iron, is arranged to slide into this tank from the top and rests upon angle irons screwed to the tank sides. Its function is to catch the pieces and prevent them from settling to the tank bottom, and it also makes it easy to remove a batch of work. A bottomless box of sheet steel is shown at C. This fits into the wire-bottomed tray and has a number of rods or wires running across it, their purpose being to break up the mass of material as it comes from the carbonizing box.
Below the wire-bottomed tray is a perforated cross- pipe that is connected with a compressed-air line. This is used when casehardening for colors. The shop that
(36)
CASEHARDENING SMALL-SHOP STEELS
has no air compresser may rig up a satisfactory equiva- lent in the shape of a low-pressure hand-operated air pump and a receiver tank, for it is not necessary to use high-pressure air for this purpose. When colors are desired on casehardened work, the treatment in quenching is exactly the same as that previously described except that air is pumped through this pipe and keeps the water agitated. The addition of a slight amount of powdered cyanide of potassium to the packing material used for carbonizing will produce stronger colors, and where this is the sole object, it is best to maintain the box at a dull- red heat.
The old way of casehardening was in nine shops out of ten to dump the contents of the box at the end of the carbonizing heat; in fact, this plan still exists in many shops that should know better. Later study in the struc- ture of steel thus
O Untreated Steel Fine grained and "tough, 0./5toO.ZO% Carbon
Carbonized at 1700 Deaf: Quenched in Water
Casf60%to90% Carbon Case hard and brrtf/e Core coarse grained a/id brittle, W5& 0.20% Carton
Case hardened on Carbonizing heat
Reheated to 1750 Deg.T Quenched in Water
Case80% to90%Carbon
Case bnttte and very hard
Core fine grained ana1 tough, 015%to 0.20% Carvon
Reheated to refine the Core
Reheated to 1500 Deg. F Quendhed in Water
treated has caused a change in thjs pro- cedure, the use of automobiles and al- loy steels probably hastening this result. The diagrams repro- duced in Fig. 2 show why the heat treat- ment of casehardened work is necessary. Starting at A with a close-grained and tough stock, such as ordinary machinery steel containing from 15 to 20 points of carbon, if such work is quenched on a car- bonizing heat, the re- sult will be as shown at B\ Here we have a core that is coarse- grained and brittle and an outer case that is fine-grained and hard, but is likely to flake off, owing to the great difference in struc- ture between it and the core. Reheating this work beyond the critical temperature of the core refines this core, closes the grain and makes, it tough, but leaves the case very brittle; in fact, more so than it was before. This is remedied by reheating the piece to a tem- perature slightly above the critical temperature of the case, this temperature corresponding ordinarily to that of steel having 'a carbon content of 85 points. When this is again quenched, the temperature, which has not been high enough to disturb the refined core, will have closed the grain of the case and toughened it. Thus, instead of but one heat and one quenching for this class of work, we have three of each, although it is quite possible and often profitable to omit the quenching after carbonizing and allow the piece or pieces and the case-carbonizing box to cool together, as in annealing. Sometimes another heat-treatment is added to the foregoing, for the
••Case S0%to90% Carbon -Case tough and hard
Core finegrained and tough,/5%'to20% Carbon
to toughen the Case,
FIG. 2. WHY HEAT TREATMENT
OF CASEHARDENED WORK
IS NECESSARY
purpose of letting down the hardness of the case and giving it additional toughness by heating to a tempera- ture between 300 and 500 deg. Usually this is done in an oil bath. After this the piece is allowed to cool.
It is possible to harden the surface of tool steel extremely hard and yet leave its inner core soft and tough for strength, by a process similar to casehardening and known as "pack-hardening." It consists in using tool steel of carbon contents ranging from 60 to 80 points, packing this in a box with charred leather mixed with wood charcoal and heating at a low-red heat for 2 or 3 hr., thus raising the carbon content of the exterior of the piece. The article when quenched in an oil bath will have an extremely hard exterior and tough core. It is a good scheme for tools that must be hard and yet strong enough to stand abuse. Raw bone is never used as a packing for this class of work, as it makes the cutting edges brittle.
CASEHARDENING TREATMENTS FOR VARIOUS STEELS
Plain water, salt water and linseed oil are the three most common quenching materials for casehardening. Water is used for ordinary work, salt water for work which must be extremely hard on the surface, and oil for work in which toughness is the main consideration. The higher the carbon of the case, the less sudden need the quenching action take hold of the piece; in fact, experience in casehardening work gives a great many combinations of quenching baths of these three materials, depending on their temperatures. Thin work, highly carbonized, which would fly to pieces under the slightest blow if quenched in water or brine, is made strong and tough by properly quenching in slightly heated oil. It is impossible to give any rules for the temperature of this work, so much depending on the size and design of the piece; but it is not a difficult matter to try three or four pieces by different methods and determine what is needed for best results.
The alloy steels are all susceptible of casehardening treatment; in fact, this is one of the most important heat treatments for such steels in the automobile industry. Nickel steel carbonizes more slowly than common steel, the nickel seeming to have the effect of slowing down . the rate of penetration. There is no cloud without its silver lining, however, and to offset this retardation, a single treatment is often sufficient for nickel steel; for the core is not coarsened as much as low-carbon machin- ery steel and thus ordinary work may be quenched on the carbonizing heat. Steel containing from 3 to 3^/2 per cent, of nickel is carbonized between 1,300 and 1,400 deg. F. Nickel steel containing less than 25 points of carbon, with this same percentage of nickel, may be case- hardened by cooling in air instead of quenching.
Chrome-nickel steel may be casehardened similarly to the method just described for nickel steel, but double treatment gives better results and is used for high-grade work. The carbonizing temperature is the same, between 1,300 and 1,400 deg. F., the second treatment consisting of reheating to 1,400 deg. and then quenching in boiling salt water, which gives a hard surface and at the same time prevents distortion of the piece. The core of chrome- nickel casehardened steel, like that of nickel steel, is not coarsened excessively by the first heat-treatment, and therefore a single heating and quenching will suffice for ordinary work.
(37)
Taking Small -Shop Temperatures
BY JOHN H. VAX DEVENTER
SYNOPSIS — The small-shop man is not inter- ested in abstract theories. But if an appliance, tool or instrument will help him make more -money or produce a better product, he wants it. This article deals with pyrometers from the small-shop users' viewpoint.
Why does an Indian decorate himself with feathers and war paint, a doctor write prescriptions in hog Latin, and a scientist cover up a new grain of knowledge with a
name that has been dead and buried for ten thousand years? Not because any one of these individuals has a grudge against the small-shop owner, but because each is instinctively following one of the three inherited prin- ciples of the preservation of prestige. The Indian is put- ting up a physical bluff — decorating his body so that he will appear imposing. The scientist is putting up a mental bluff — decorating his discovery with a name that will be hard for common people to pronounce and under- stand. The doctor is not bluffing at all — he is just keeping business in the family, and the worst part of it is that all three of these fellows get away with it!
VARIOUS TYPES OF PYROMETERS SUITABLE FCR USE IN THE SMALL SHOP
F — Brown base-metal thprmocouple with bent mounting. G —
A — Le Chatelier portable thermocouple pyrometer. B — Hoskins portable pyrometer. C — Bristol portable thermo- couple pyrometer. D — Englehard for lead pots, etc. E — Hoskins
Le Chatelier rare-metal fire end mounted
arch of heating
portable bent mounting furnace. H — Brown expansion pyrometer mounted in tinning base-metal thermocouple bath. J — Bristol gas-expansion recording thermometer mounted
with indicator and recorder and water-cooled cold end. for temperatures of fluid under pressure.
(38)
TAKING SMALL-SHOP TEMPERATURES
I believe that a man who invents a new machine or appliance • and then goes back to the Dark Ages to find a name for it is unconsciously handicapping its sale and use. The name conveys the impression that the thing itself is highly scientific and thus erects a barrier of exclusiveness. Of course if it is something that people need, the demand for it will in time overcome the handi- cap of the name, which will become familiar; but never- theless the handicap exists at first and is an unnecessary tone. Take, for example, tachymeters, scleroscopes and pyrometers — one of a bashful and retiring disposition might hesitate to make the acquaintance of such high brows, whereas he would be glad to shake hands with a " speed gage," " hardness tester " and " heat gage."
This may be one reason why the measurement of temperatures in small shops is not as thoroughly under- stood as it should be. It takes time for instruments which originate in the laboratory to filter down to the level of small-shop practicability. But I venture to predict that 20 years from now the pyrometer will be as familiar and well understood a small-shop tool as is the micrometer at the present day.
Twenty years ago a micrometer was seldom found in a small shop. Nowadays you seldom find a small shop without one. Progress has made it necessary to work to close limits of size, and the use of proper size-measuring instruments followed this as a natural result. With later progress has come the refinement of materials which calls for some means to measure temperature as the micrometer measures diameter.
OLD MAN JONES, OF LANCASTER — AN OPTIMIST
Old Man Jones, of Lancaster, took a contract for some machines, among the parts of which were a number of nickel-steel heat-treated gears. He never had handled any alloy-steel work in the past, but had a blacksmith who was a crackerjack at hardening springs and cutting tools. Jones, being a progressive chap, determined to meet and get acquainted with the alloy-steel proposition, as he could see considerable business for one able to handle it. After careful machining, the gears were handed over to the blacksmith for heat-treatment. This gentle- man was not as optimistic on the subject as Old Man Jones but said that he would do the best he could. The heat-treatment specified was to heat these gears to 1,550 deg., quench, reheat to 1,350, quench, and reheat to 800 deg., after which they were to be slowly cooled.
The first act of the worthy smith was to look up a color chart and translate the heat-treatment temneratures into colors instead of degrees. He found that 1.550 deg. F. represented a medium cherry red, 1,350 a dark red, and 800 deg. the lowest visible red. It was really as easy as matching shades of silk in a dry-goods store with- out the samples!
The furnace was a small one, and as a result the job had to be divided into several batches which were senarately heated. When they were finished, the gears all looked much alike except that some had a little more scale than others. They rang the same when tapped with a hammer and seemed to give the same amount of pull upon a smooth file.
Old Man Jones and his blacksmith tried almost every- thing they could think of to test those gears, except biting a piece out of each of them. They were sure that they had a good job, but the customer's inspector did not
seem willing to take their view of the matter. He put the gears under a strange-looking instrument that was a cross between a thermometer and an atomizer and declared that twenty-three out of thirty-five would not pass the required hardness test.
" Why don't you fellows get a pyrometer and know what you are about ? " he asked Old Man Jones. Then being a decent sort of chap and seeing that he might as well have asked Jones why he did not keep an ichthyosaurus in his backyard, he explained what a simple instrument a pyrometer really is.
" What you need in your shop is a thermocouple pyrome- ter," said the inspector, " which is nothing more than a couple of wires running from an indicator and joined together within the furnace. When the joined end of the wires is heated, you look at the indicator and read off the temperature. The thing is really as simple as a ther- mometer and a good deal easier to read."
VARIOUS PYROMETERS AND AN IRISHMAN
There are a number of kinds of pyrometers besides those made on the thermocouple principle. Some depend on the pressure exerted by a gas inclosed in a tube. There is an accurate type known as the " resistance pyrometer," which is a bit too complex for the average small shop. There are radiation and optical pyrometers which look like telescopes and are simply pointed at the hot objects. They are most suitable for work above 3,000 deg. F., for no part of the apparatus itself is heated.
The instrument shown at H in the illustration is an " expansion pyrometer." It works on the difference of expansion of graphite and iron rods in its stem, and its upper working limit is 1,500 deg. F. I recall an experience with one of these instruments and with an Irishman named Pat, who was engaged to run the galvanizing department of a large upstate machine shop. The man- agement of this plant had decided to have everything up to date and so got a pyrometer for Pat, without knowing that his education had not gone as far as reading either words or numbers. Pat, however, was too foxy an indi- vidual to give this fact away. Suspecting it and wishing to have a little fun with him, I asked him one day what temperature he was carrying on the galvanizing pot. Quick as a flash the answer came back, " Sure you have got spectakils on; you can see it twice as aisy as me! "
The thermocouple pyrometer, which is the one for the small shop, is made in a great variety of styles and in two general classes, portable and permanent. The first kind, as the name indicates, can be carried about from place to place and used to take the temperature of almost anything in the shop except a feverish haste. The second kind is installed in a lead pot, heating or annealing fur- nace or other place where it is desired to keep a continual check on temperatures.
WHAT CONSTITUTES A THERMOCOUPLE PYROMETER
The parts comprising a base-metal thermocouple pyrome- ter are shown in the illustration at K. The arrange- ment does not look formidable, and indeed it is about as simple an instrument as could be devised. It con- sists of a couple of wires of unlike material which are twisted and welded together at one end. At the other end they are connected through an electric-wire circuit with a simple indicating instrument exactly similar to a voltmeter, except that it registers degrees of
(39)
MAKING SMALL SHOPS PROFITABLE
temperatures instead of volts. When the welded end of the couple is heated, an electric current is set up by which the degree of heat may be measured. Fire ends are of two general kinds. One kind is known as the " rare metal " thermocouple and is used for the high temper- atures between 1,800 and 3,000 deg. F. The other kind is known as the " base metal " thermocouple and is made of more common and less expensive material, which, however, will not do for continuous service over 2,000 deg. F.
The fire ends of thermocouple pyrometers are protected by sheaths of various materials, according to the service and the degree of heat. Porcelain tubes are used for the highest temperatures, In a lead bath an iron sheath or seamless-steel tube is used with a nickel-plated envelope above the surface of the metal to protect against vapors. Firebrick tubes are sometimes used for annealing fur- naces, and graphite or clay tubes are used for measur- ing melted-metal temperatures. The protecting tubes should project into the furnace or the melted metal at least six inches.
AT THE OTHER END OF THE WIRES
Two kinds of instruments are connected to the fire ends of either of the foregoing types — -indicators, which indicate temperature, and recorders, which make a con- tinuous graphical record similar to that made by a record- ing pressure gage or recording wattmeter. An instrument of each kind may be attached to the same fire end and will register its temperature simultaneously, one indi- .cating and the other recording. Again a number of fire ends in various furnaces may be attached to the same indicator and recorder by means of