Practical pattern making ...

Front matter

Class /.

-^1

Book GopvTightl'

Preface

In presenting this new edition of Practical Patternmaking, we have endeavored to make the book more attractive and interesting by the addition of new material at places which seemed somewhat incomplete.

The substitution of this new text for such part of the old volume as, in our opinion, was of less interest to the patternmaker, improves the general tone, and makes the entire book more useful and instructive to the trade.

The specific examples, which could easily be increased in number, there being no lack of material, if the size of the work did not restrict their number to the allotted space, have been selected with the purpose of making the ones given of as great scope as possible, that they may be of wider appHcation; thus making this part cover a larger field of pattern work.

All technical books must necessarily be only a more or less incomplete record of results attained by the efforts of the individual in the line of work or study to which the book is devoted. It is obviously impossible to make any such record entirely complete in a single volume; and in selecting the material for a book of this kind, much that is desirable must be discarded, retaining only the best, or that which seems, in the judgment of the author, to be of the greatest benefit to the average tradesman.

If the inteUigent reader, making due allowance for lo PREFACE.

lack of space, finds that this book seems to cover the field of patternmaking thoroughly, giving satisfaction to those seeking information, and interesting those who are willing, or pleased, to learn from the experience of others, then we shall feel that our time has not been wasted in useless effort.

Many of the subjects illustrated and discussed in this treatise originally appeared in the columns of the "American Machinist," others were published in ''The Patternmaker." And in ''Wood Craft," and "Castings," the worthy successors to "The Patternmaker," appeared the new material used to make this edition more presentable. To these publications we are indebted for the courtesy extended.

Firm in the beHef that this revised edition will find favor in the eyes of my fellow craftsmen, I am,

Yours very truly.

F. W. Barrows.

Part First. Introductory

CHAPTER PAGE

I. Patternmakers and Patternmaking 15

II. How Some Folks Make Patterns, 20

III. Some Methods, . 24

IV. Patternmakers, 27

Part Second. Material And Tools

I. Lumber, 31

II. Varnish, 35

III. Miscellaneous Materials, 39

IV. The Bench and Its Attachments, 43

V. Hand Tools, 47

VI. Bench Work, . . • 51

VII. Machine Tools for Patternmakers, 53

VIII. The Band-saw, 56

IX. The Circular Saw, 62

X. The Lathe, 80

XI. Fillets, 96

XII. Stavework, 99

XIII. Cant or Segment Work, 106

IZ

12 CONTENTS.

Part Third. Some Examples Of Wood Patterns

CHAPTER PAGE

I. Patterns for Belt Pulleys, 113

II. Patterns for Cable Pulleys, ........ 120

III. Making Patterns for Chain Wheels, 130

IV. Patterns for Steam Cylinders, 139

V. One Way of Making a Crosshead, 153

VI. Making Gear Patterns, 158

VII. Propeller Wheels 176

VIII. Patterns for Screws, 189

IX. Traction Wheels for Farm Engines, 205

X. Globe-valve Patterns, 208

XI. An Example in Projection, 225

Chapter I. Patternmakers And Patternmaking

If there should be as much time and skill devoted to the search for the original patternmaker as has been displayed in the search for ancestors who may be exhibited without detriment to our present social and moral standing, it would perhaps be found that he was known among his neighbors as the best man to build that new house for the mayor, or the sty for Farmer Jones' pigs, and, in fact, anything wanted, which was constructed principally of wood.

Perhaps it was a plough which first demanded the services of a patternmaker, and as the plough had always been made of wood and constructed by the party mentioned above, what more natural than to employ the same capable individual to construct the desired pattern ? Or, what is still more probable, that this same talented man, whose many accomplishments have been handed down through generations to the present skilful members of the trade, originated the pattern idea and used one of his own wooden mouldboards for the first pattern. Some of the castings made to-day look as if the original pattern were still in use.

IS

Later, as the wood-workers became divided into classes, each individual following that particular branch which liking or necessity dictated, it seems to me most probable that each branch would be called upon to construct such patterns as might be needed for castings used in their line of business. With the demand for castings constantly increasing, the moulder commenced to be heard, and the sound of his voice has never since ceased.

Men began to see that, whatever the casting, there were certain rules to be followed in the construction thereof: it must have draught, and the shrinkage of the casting must be allowed for. Even at the present day, if these simple rules are transgressed, it causes the moulder to grieve and the man who pays to swear.

As you couldn't reasonably expect every wood-worker to know about these little things, the pattern work would naturally come to such as had shown their ability to construct useable patterns; this man would soon have work enough to keep him busy on patterns alone, and as a consequence the patterns would improve.

As the struggle to produce more castings grew intense and it became necessary to have better castings, and more of them, the wood patterns were not substantial enough, or perhaps the wood pattern was used up, and some genius hit upon the happy idea of using one or more of the castings already made for patterns. The next step was that the moulder, who is ever watchful of the master's interests when it happens also to be his own, suggested the gating of the patterns, having noticed the castings as he dumped the mould, with their runners tying them all together, making one pattern of the flask full. This shifted a portion of

PATTERNMAKERS AND PATTERNMAKING. 17

his own work upon the patternmaker. To be sure, he got better castings and more of them, but this was entirely the result of the patternmaker's efforts.

Still the demand for more and better castings at lower prices would not be satisfied. As a result of the effort to supply this demand, we have now the moulding-machine, and a good many of them, which will do anything that the moulder can do and do it in a very superior manner, so the advertisements say. The moulding- machine lowered the cost, as the patterns are so arranged that less skill is required of the moulder, thus making possible the employment of cheaper help in the foundry, increasing the output and decreasing the cost of production.

So we have advanced from the crude, inaccurate wood pattern, made by the wood- chopper of prehistoric days, to the highly finished metal patterns now required for the moulding-machine, and from the all-round individual of that time to the highly specialized patternmaker of to-day. The patterns that are constructed of wood, by the skilled members of the craft to-day, show evidence of good judgment in the selection and arrangement of the material, although there are some of us who are inclined to think that if the making of the wood were intrusted to us we could produce a very superior article in this line, and one which would be less subject to the influence of the weather. However, the man who constructs the pattern for some light, frail piece so that it gives good service and keeps its shape, is still entitled to some credit for so doing.

The durability of the wood pattern depends greatly upon the wise selection of material, and by this I don't mean the kind of material, because this is usually dictated by the firm, or by the foreman; but if the entire stock of lumber is Hmited to two boards, there is a choice between the two, and it is in making this choice that the expert shows his skill. Sometimes, it must be confessed, it seems as though each one of the two was a little poorer than the other.

For large patterns or such as will be used but a few times there is probably nothing to be had better than white pine, while for small and medium-sized pieces, especially if they are to be much used, a harder wood is better.

Many prefer cherry; for myself, I prefer mahogany, and for light, thin patterns would use what is known as Mexican wood. For short, thick forms, especially such as may be made almost completely in the lathe, Cuba wood is best. Whatever the material, it must be thoroughly seasoned, and from old trees in preference to young timber, as young timber, while it is usually much harder, is also much more liable to spring and twist.

In assembling the pieces which go to make up the complete pattern, glue is much used; here again experience counts, and even the boy has found that it is quite a knack to make glue joints that are really substantial. Wherever possible, glue joints should be nailed or strengthened with screws. Loose pieces are sometimes necessary on wood or metal patterns, but it is a good rule to make them as few as possible. They add to the cost and are often the cause of poor castings.

Many shops use two colors of varnish, one for core prints and another for the body of the pattern. This is probably a good plan if not carried to extremes, as in the case of some regular stock pattern which is in use pretty much all the time. The moulder doesn't need to be con-

PATTERNMAKERS AND PATTERNMAKING. 19

tinually reminded that he must set a core in this mould, and the patternmaker can employ the time saved to much better advantage.

After the first coat of shellac is the proper time to wax or putty a pattern. This operation often gives more satisfaction if the whole job can afterward be covered with black varnish, for black varnish, like charity, covers a multitude of sins. Putty will probably wear longer, but it isn't quite as nice to handle, and doesn't harden so quickly as wax, although when it has set it is much harder. Beeswax, unless it is pure, and put on hot, will not adhere to a wooden pattern.

When we come to metal patterns, the master pattern, if one is required, is generally of wood, thus calling for the services of the woodworker, and the castings for gating are usually of brass; so the brass finisher, with his knowledge of soldering, is called upon to finish and gate the castings. Thus was the original metal patternmaker drawn from the ranks of the brass finishers. To-day the competent metal patternmaker is called upon to finish not only brass patterns, but also those made of cast-iron, aluminum, steel, and wrought-iron. He must also be familiar with the use of machine tools, the lathe, the planer, milling-machine, and drill press. So that the patternmaker of to-day may be said to have added to his previous knowledge of mechanical drawing, woodworking, moulding, and brass finishing, no small part of the machinist's trade.

Chapter II. How Some Folks Make Patterns

There are about as many different ideas in regard to the construction of any one pattern as there may be good ways of making the pattern. Where is the patternmaker who, in looking over patterns he knew were made "outside," has not noticed that "they don't do their work as we do " ? This only shows that your way is not the only way, and very likely not the best way of doing the particular job under inspection.

Now, as a pattern is only a "means toward an end," which end is not always in the foundry, although a good many patterns are here brought to an early and untimely end, we should not consider the pattern of more importance than the end for which the pattern is made. This is sometimes the case with those who think that the moulder is simply a machine which, if supplied with any kind of a pattern, is bound to turn out a good casting. Moulders have some ideas in regard to moulding patterns which the patternmaker should respect; and if he would try to construct the pattern so that it would mould according to the moulder's ideas of right, I think that all hands would be better pleased with the result. The great idea is to get a nice casting, and where the patternmaker and moulder work in harmony this is usually accomplished.

HOW SOME FOLKS MAKE PATTERNS. 21

The patternmaker certainly has the right to criticise his own work, and perhaps the work of any of his fellowcraftsmen; but let his criticisms stick to hard facts, and not be based on prejudice, as I am afraid is apt to be the case. I have noticed, and so have you, I presume, that when some outside pattern has found its way to our shop, how many faults we seem to see in it. Perhaps the whole gang will get after it in this style : There is a pattern which Overtheway & Co. have made, and it has been sent to our shop to mould, and has found its way to the patternmaker. If it is a new pattern, any of the help can see that it is a stranger as soon as they set eyes on it; then see how it will be criticised. Perhaps away down in our minds we can see that it is a neater-looking, better-constructed job than we ever made, or could make; still let us see if we can't find some fault in it.

Yes, there it is — "See that short grain?"

"How long do you suppose that will stand in the sand?

They hadn't ought to have put in that short grain."

There was really no way to avoid the short grain in this case, perhaps, but that makes no difference ; we set out to find some weak spot in this pattern, and we are bound to do it, and as long as no one has the courage to speak for Overtheway & Co., their reputation as first-class workmen will suffer in the judgment, or, more correctly, in the conversation, of present company.

"Here's another thing — a 2" core print that just fits the box. "

"We always make the print a little larger because you know the core will swell a little in baking — at least, that 10" cylinder pattern I made, I left the core print a little full, and the moulder said it was all right, and of course a 2" print will swell the same in proportion to its size."

Yes, that is the reason that none of your small work ever has the holes cored out in just the right spot. The core will always go to the top of the print and perhaps it will twist over one side a little. You have always laid the blame on the moulder's shoulders, when by a little experimenting you would have found that a 2" core would, if the sand wasn't too rich, just fit the box after baking, and consequently a print ]ust the size of the box would be ]ust right for the core. But as we are bound to condemn this pattern, don't mention this.

"Look at those fillets — just a little three-cornered piece which cuts off the angle of 90° but leaves two in its place of 135° each. This, any one (of the present company) can see is bad practice, because what is a fillet good for if it doesn't do away with angles ? " As for me, I would rather see this kind of a fillet, or corner, put in neatly (as in the present case) than to see some of the fillets that pretend to be a quarter circle, more or less, but are really no nearer the ideal fillet in shape than the present specimen.

Now, see here, what is a fillet used for ?

"To strengthen the casting or to prevent shrinkage in a place that would weaken the casting, or look bad, and it may be used to make the moulder happy, if you think he deserves it."

Correct; and doesn't the present specimen fill all of these conditions ? There is really only one fault about it. It isn't a quarter circle, but see how much easier it can be made and put in than a regular fillet — no feather-edges to break off — and after it is in place there will be no feather-

HOW SOME FOLKS MAKE PATTERNS. 23

edges to roll up. In short, it is really better, so far as durability goes, and just as good in every other particular, except perhaps in regard to looks, and this, very likely, is only a cultivated taste like smoking, for instance. I presume that the casting will be just as strong as though the fillets were all perfect arcs.

''And now here is one more thing. See this chalkmark, *2off '? That means two castings wanted from this pattern. See how cheaply we have sold ourselves ? Here is a pattern that we haven't been able to find any really serious fault in, even though our criticism was founded on prejudice, and was all on the supposition that this pattern was intended for a first-class job, and here is the proof that it was intended for two castings only. We shall have more respect for Overtheway's work after this."

Now, be honest, and own up that this criticism, or rather this fault-finding, we have been indulging in, was nothing but prejudice. This is very apt to be the case with all criticism. We condemn others' ways of doing work only because they are different from our own, when in many cases our way is the one that would be condemned by a fair judge.

If you wish to be at the head of your trade, strive to adopt all of the best ideas. If your own work won't bear comparison with Overtheway's, why, condemn your own and try to improve on their ways.

If you are so short-sighted as to stick to your own way after you have found that it isn't the best way, or are so bigoted that you can't see any faults in your own work and be willing to acknowledge them, I am pretty sure that you will be left far behind in the race.

CHAPTER in.

SOME METHODS.

An old patternmaker gives a method of obtaining the weight of irregular-shaped castings by immersing the pattern in water, measuring the displaced volume of water, and multiplying the result, in cubic inches, by .26, the weight in pounds of one cu. in. of iron.

Another thinks that it would be simpler to weigh the displaced water, or, better yet,, to weigh the pattern itself. But as the material of which the pattern is made varies so much in weight, the result would be very uncertain. Still, as the weight of water is practically constant, by weighing the displaced water he would probably obtain the desired end as accurately as by the measurement of displaced water, and more especially as an error in measurement would, in the final result, become 7.21 times greater than an error in weight.

I should consider that both gentlemen were advocating very bad practice when they suggest immersing wooden patterns in water, and would advise weighing the pattern, as the result would, in either of the three methods, be only an approximation. The difficulty arising from the varying weight of wood could be lessened by cutting a small cubical block from the same plank used to make pattern; this piece to contain 3.85 cubic inches. Then the weight

SOME METHODS. 25

of pattern divided by the weight of this block gives the weight in pounds for a solid casting from the pattern.

I find many mechanics using the sense of f eehng in making fine measurements, the articles employed being usually a steel scale and a scriber or the point of a knife. In using a pair of dividers, their setting may be tested by placing one point in a line on the scale, using it as a centre, the dividers being held nearly parallel with the flat side of scale, the legs of the tool as nearly parallel with the Hnes as possible; then if the other leg is slowly brought down to the required line, the spring, or lack of spring, noted by the sense of feeling, as the other point enters the required line, will show whether they are correctly adjusted. There are some things that we can see better with our fingers than with our eyes.

About scales, when the drawing comes into the pattern shop marked "Use dimensions only," and drawn to any scale whatever, there are usually many points which will have to be scaled by the patternmaker, and if the scale of the drawing is such as can be measured by the ordinary steel rule it saves much arithmetic and — talk.

Imagine the patternmaker getting a drawing marked "|In. = I In." and then having to figure out all of his measurements to this scale. The fact that this scale made the drawing fit the standard size sheet doesn't seem to me of enough importance to warrant the risk of condemning the patternmaker to everlasting punishment by its use.

An old friend of mine was in the habit of classing the graduates of our technical schools, or such of them as were privileged to add M.E. to the name given them by their parents, as ''pyrotechnic" engineers, and I sometimes think that his title wasn't so far off after all, for the "pyrotechnic" engineer might be expected to produce, as he sometimes does, "pyrotechnics," as witness the language of the patternmaker in the case cited.

The patternmaker, if he is so inclined, may, by consultation with the draughtsman or with the designer, assist in eliminating some faults of construction as regards the pattern or the casting; and no fair minded, conscientious draughtsman will take offense at honest criticism of this kind.

Chapter IV. Patternmakers

Patternmakers may be considered as toolmakers for the foundry, and as the so-called toolmaker needs to understand the machinist's art in all of its details, so the patternmaker, to be of any real use, must understand the moulder's trade, in order to make the special tools or patterns without which no castings could be produced. He should not only be competent to produce patterns for staple goods, but must continually be making new articles, or old ones in a new form.

To this end he must be able to read mechanical drawings, and he is, in fact, constantly expected to read so-called drawings which are far from being mechanical and which, like Johnny's picture of the cow, would be unrecognizable without the title, which title is perhaps the only clew to the meaning of the drawing.

Behold, now, the patternmaker in the r61e of Sherlock Holmes ; the draughtsman (?) may have as crude an idea of the article delineated as the boy had of the horse, which he described as an animal with a tail and four legs, one at each corner; still, if S. H. is in any sense worthy of the name of patternmaker, he will be able to follow the " clew" through the drawing, and point out the tail, and each of the four legs, and then to join them all together in a more or less complete and artistic whole.

Speaking of drawings, I am reminded of an old acquaintance who consented to give a young friend instructions in mechanical drawing, and did so, the complete course in one lesson, by instructing the pupil in the following words : ''Make all the lines you can see, full lines, and those which you can't see, broken lines. That's all there is to it."

After absorbing all of the information given by the drawing, the patternmaker usually makes a full-size lay-out of the piece to be made. He must now study the shape of the piece, and plan to so construct his pattern that the resulting piece of work will be strong and serviceable, and enough like the drawing that it will not, like Johnny's cow, require to have the name printed on in order that it may be recognized by its creator — the pattern, not the cow.

This faculty of being able to see things before they exist — and, by the way, this is different from the faculty for seeing imaginary things, which may be acquired by frequent internal applications of the contents of the alcohol jug — this faculty is, I say, one of the necessary qualifications of a good patternmaker.

Without this skill, or foresight, the pattern becomes a freak job, and the only way to save it from the scrap-pile is to make up the bad spots with beeswax and give it a heavy coat of black varnish.

Chapter I. Lumber

For the general line of pattern work there is probably no better material to be found than white pine. White pine is light, easily worked, takes glue and varnish nicely, and is fairly durable. As there are many patterns made for present use only, these points cannot be overlooked, else the labor cost gets too high.

When I say that white pine is easily worked, I mean that it not only offers little resistance to cutting tools, but that it is not "hard on tools." A nicely seasoned piece of old timber can be sliced off by a sharp chisel or gouge with a faciHty only to be equalled in cutting whitewood timber. The tool, when cutting pine, does not dull very quickly, which makes it a pleasure to work this timber.

Whitewood has the serious objection of being too susceptible to atmospheric changes. It also seems to be always shrinking; in short, one of the earlier settlers in Ohio said that there was a great deal of whitewood timber in that country; he himself had cut a tree which squared 24" for twenty feet in length. This log he had sawed into planks and used for a floor in a 20 x 30 building. It took just fifteen planks to cover the floor, "but the plaguey stuff shrunk so fast that I had to put in one new plank each year, and in fifteen years I had an entire new floor."

Shrinkage and swelling of timber is caused by atmospheric changes; temperature and moisture, or lack of moisture, both having some effect. Increase of temperature, without a corresponding increase of humidity, will always cause shrinkage, while an increase of moisture invariably causes an increase in the size of the piece of timber under consideration, the expansion being greatest in a radial direction — this radial direction referring to the position of the plank in the log, which can be easily determined by examination of the cross section. As all timber grows in concentric layers, it is evident that a radial line (of the tree) must always be at right angles with these layers.

Again, as all timber is porous, and as these pores, or pipes, run lengthwise of the log, and in the green, living tree are filled with liquid, the evaporation of which seasons or dries the timber, causing at the same time shrinkage, it is evident that the fluid near the ends of the log will evaporate fastest, and thus the ends will season, or shrink, first, the shrinkage strain often causing timber, both logs and planks, to crack at the ends.

Moral : Don't put green or water-soaked lumber in the drying-room.

Temperature, and perhaps moisture, causes a change in the length of timber; higher temperature causing expansion, which is partly offset by the changes due to increased evaporation of the contained moisture. In the case of "cross-grained" timber, it is evident that the same conditions which affect the width of a board will, in a lesser degree, affect its length.

This question of shrinkage — or, more correctly, the neglect of it — has ruined many an otherwise good job. At

LUMBER. 33

its best, wood is very sensitive to moisture and should not be exposed to its influence.

In mahogany we have a timber which, having a hard, dense surface, is invaluable for small, fragile patterns or for patterns which are in constant use. It is more difficult to work than pine, and doesn't take varnish and glue so readily, but it will stand lots of abuse.

In selecting mahogany for patterns, use only the straightgrained timber. Mexican or Cuba wood is best, what is known as baywood being but little, if any, better than pine.

Mahogany, being very close-grained, is not so susceptible to atmospheric changes as pine. This statement is perhaps unnecessary, as any close-grained timber is proof against slight changes in temperature and humidity; because the term "close-grained" means small pores, and we all know that it is hard to force moisture through small holes, with only the slight variations in pressure caused by atmospheric changes. Therefore, let us use some kind of close-grained timber for such patterns as are expected to bear hard usage. And for the same reason that the old farmer ''didn't care what color the new school-house was painted, so long as it was red," let us use mahogany; you can't find any better (color) timber.

Cherry has proved itself of value in making durable patterns ; in fact, many (otherwise) good patternmakers prefer it to mahogany, and it is cheaper. It is hard, but not so nearly immune to the influence of temperature and humidity as mahogany.

On the whole, cherry is very good pattern material, the item of price, with its other good points, making it a strong rival of mahogany. One very important point in 3 cherry is this : Don't use young timber or you will suffer remorse.