A high school course in wood pattern making

Preface

This book is the outgrowth of seven years of teaching experience in both Trade and High Schools. The author submits the book on the ground that we can all benefit by the experience of others. Works on Pattern Making are not as numerous as the importance of the subject warrants.

The various articles in this book follow each other in what seems to the author to be the natural sequence. To begin the subject the teacher lectures on The Metal Trades (Chapters I and II), and the manufacture of iron products, so that the pupil can learn exactly what part pattern making plays in the commercial world. Then the wood working exercise in Chapter III should be started. Before beginning it, however the pupils, as a class, should be made to remove the plane bit and sharpen it and learn to replace it correctly. Pupils dislike to take a plane apart until the teacher proves to them that it is a simple operation.

While the pupil is working on the exercise, certain periods should be devoted to lectures and recitations on Moulding and Pattern Making, (Chapters IV and V,' so that these chapters are covered by the time the exercise is finished. Then the student will understand and can begin making the simple patterns in Chapter VI. If lathes are scarce in the shop some pupils may be put at turning immediately after the first pattern. These pupils can then go back to the bench while others are turning. From parted patterns, to the end, the time spent on the bench preparing the pattern for the lathe, making the core box and finishing, exceeds the time spent at the lathe and a student need never be idle while waiting a chance to get on a lathe. Each student must have a bench.

Each individual kit of tools should be as small as possible. Large kits are difficult to keep track of. Each boy needs only : bevel, square, back saw, gage, scribe, dividers, rule, dust brush, jack plane, block plane, y 2 " chisel, i" chisel, fy" inside gouge, and Y" outside gouge. Sharpening outfits must be as convenient as possible. If possible supply each bench with an oilstone.

Other tools are necessary but as they are not frequently used, a few of each may be kept in a convenient wall cabinet. There should be at least one-third as many lathes as there are pupils in the shop at one time and as many face plates as there are pupils taking the course. A band saw is indispensable.

Experience gained while a student at the Williamson School of Mechanical Trades enabled the author to arrange the course and his ten years experience as a pattern maker in large commermercial shops enabled him to present actual shop methods.

Hand Wheel. Gear Blank, Arms, Gear Wheel. CHAPTER XII— Staves and Strips 103

Flange Pipe, Stripped up Core Box, Loose Pieces. Cylinder Cover.

Chapter I. The Metal Trades

As you walk along the streets of a city and observe the ornamental lamp posts, the U. S. mail boxes, or the fire plugs, or, as you hear the bell or whistle of a locomotive or the chug-chug of a gas or steam engine, has it not at some time excited in you a curiosity to know the processes by which such things come into being? Did it ever occur to you that the motor in your father's automobile, the parts of your mother's sewing machine, the hardware in your home, the plumbing fixtures in your bath room, or the pipe fittings and steam radiators which help make you comfortable, or even the artistic bronze statues which help beautify your parks, might be produced by processes which would prove to be a great deal more interesting to you than anything into which you have yet inquired? It is the purpose of these pages to get you interested in this art ; the art of manufacturing metal objects, such as those mentioned above, and countless others.

To begin at the beginning, let us follow the manufacture of some new machine.

Your History has taught you that some clever men such as Watt, Whitney, and Fulton, first perfected certain new commodities, which were of great benefit to mankind. You call them inventors. In those days inventions were produced only after long and tedious experiments with moving models. Nowadays when an inventor conceives a new machine, he sets it down on paper. He figures out its moving parts and their required strength, etc., often without attempting to make a working model. The result is a "drawing." With this drawing he tells others what has been in his mind. Drawing is the universal language of the engineer.

The inventor may not have an engineering education. In that case, he is obliged to employ an engineer to design his machine. After the designer has proportioned the parts, the draftsman draws the details accurately to scale and then a tracing and blue prints are made.

The blue prints are sent to a pattern maker, who reads them and fixes in his mind the idea that the designer intends to convey. He then proceeds to fashion certain forms in wood somewhat resembling the parts of the new machine. These forms are called patterns.

The patterns are then sent to the foundry where a workman called the moulder buries them in a special kind of sand and packs the sand hard around them. Then by ingenious methods, which have been anticipated by the pattern maker, he withdraws the pattern from the sand, leaving the full impression of the pattern in the sand. This impression is called the mould.

While the moulder is preparing the mould, the foundryman is firing up his cupola in which he melts bars of pig iron and quantities of scrap iron. When the iron is brought to a molten state, he rams a clay plug out of a tap hole near the bottom of the cupola, letting the molten metal flow down through a trough into a clay lined ladle in which it is carried to be emptied into the mould.

When the metal has cooled and is dug out of the sand, it is found to have the shape that was planned for it by the pattern maker and is called a casting.

To free the casting from the particles of sand which adhere to it, it is sent to the cleaning department, where it is tumbled around in a large revolving cylinder called a tumbling barrel or it is subjected to other treatment. The cleaned casting now goes to the machine shop.

These castings are somewhat rough ; so in order that the parts of the machine we are building can run smoothly together, we must finish them off smooth on the surfaces which come into contact with each other. To that end, the machine shop is equipped with drill presses and boring mills for boring holes, lathes for turning cylindrical pieces, planers and shapers for making flat surfaces so that two pieces may be made to slide smoothly on one another or fit snugly together, millingmachines, and other machines whose variety and functions are too numerous to mention.

After the castings have been finished, they are sent to the assembling or erecting shop, where they are all carefully fitted together to make the complete machine.

Cast iron is brittle, and when made into slender shapes, is in danger of being broken if subjected to a shock. It is desirable to make such parts from a tougher material; therefore, wrought iron is used. Wrought iron cannot be melted in the cupola and poured into the mould. It is made red hot and hammered into the reuired shape. This work is done in the forge shop.

The student should know the above departments in their proper sequence and the function of each.

Departments Constituting a Machinery Manufacturing Plant and Their Functions

i. Drafting room: where the machine is planned and drawings made.

2. Pattern shop ; where the forms for use in making the moulds for the parts are made.

3. Foundry ; where the moulds and castings are made.

4. Forge shop ; where the wrought iron parts are hammered out.

5. Machine shop ; where the castings are finished.

6. Assembling shop ; where the machine is fitted together.

Compare this with a modern technical high school and you find that the high school is often a complete machinery manufacturing plant.

In a commercial shop the apprentice to any one of the above trades learns only his own trade. Think of the tremendous advantage you have over him since you will get a knowledge of all.

Chapter II. Benefits Of Shop Courses

You may wish to finish your education at an engineering college. Then you must know the trades, for they are the very foundation of engineering.

You may wish to be a draftsman. You will then be required to make drawings of objects that are to be made by the processes involved in these trades. Your knowledge of these processes will serve you, in that you can design the objects so that it will be possible to make them by these processes. You will be more valuable to your employer than the office trained draftsman.

You may live in a community where the manufacture of iron products is the chief industry and there is a great field for mechanics. It would be natural for you, under these circumstances, to wish to learn one of the trades and you would be apt to think the others of no importance to you. As a matter of fact, a knowledge of the other trades would make you a broader and more efficient mechanic in your own line and you would rise above the average.

In no trade, however, is a knowledge of the others as essential as in the trade of pattern making.

The pattern maker must understand mechanical drawing as well as the draftsman himself under-

In Wood Pattern Making J

stands it ; for he must not only read the drawing, but actually lay it out full size, no matter how large, before beginning the pattern. Every pattern shop possesses a stack of large and small drawing boards one of which is selected by the pattern maker who places it on a pair of horses, planes off the old drawing and proceeds to lay down a full size drawing of his new job accurately, scratching the lines on the board with a sharp scribe or knife.

It is obvious that the pattern maker must know moulding; since he must anticipate the needs of the moulder and so arrange the parts of the pattern that the moulder can draw the pattern out of the sand without breaking down any part of the mould. He must understand enough about machine shop practice to be able to act on his own account in such matters, as adding metal here or there for the machinist to plane or turn off in order to get a smooth surface on the casting. It often happens that he must decide where to put certain lugs or projections on the pattern, which do not appear on the drawing, but which are used by the machinist in chucking or centering the work in the machine.

In addition to this knowledge, the pattern maker must be highly skilful with the wood working tools in order to produce patterns which are smooth and clean cut. The ability to operate machine tools or wood working machinery is necessary. A surprising variety of work can be done on such machines by one who will take the trouble to learn how. An illustration of what can be done on the circular saw can be found in the Oliver Catalog, Students in elementary pattern work will, however, have little except plain work on these machines.

Above all, the pattern maker must possess resourcefulness and be willing to use it continually, No mentally lazy person can become an efficient pattern maker, Any number of castings can be produced by the use of a single pattern ; therefore, the pattern maker seldom has two jobs alike, Each new job calls for original thinking, planning and scheming. This thinking covers the whole range of the metal trades.

While the pattern maker works in wood, he has little in common with the carpenter and cabinet maker. His thoughts are mostly on metal. Therefore pattern making is classed among the metal trades.

From the foregoing it will be seen that in order to complete a course in pattern making hard work is requited. Your teacher has a right to expect it from you. He has a right to suppose that you want this kind of work or you would not attend a manual training school. If you lean toward business or a profession you should have attended a commercial or academic school. But the author wishes to state that one who has no intention of following a mechanical pursuit, will find that the knowledge gained in this work will give him greater satisfaction, in after life, than many other things he has learned at school.

Chapter III Woodworking

Exercise I. (See Drawing, Fig. 8.)

Most pupils who take a course in pattern making have had a course in woodworking or cabinet making in the lower schools, therefore, it is not necessary to begin at the beginning. Many bad habits in the use of tools are formed by pupils, however ; so this exercise, while it has nothing to do with pattern making, will serve as a review for the student and an opportunity for the teacher to correct bad habits before the more serious business of pattern making is taken up. As will be found later, the pattern maker's thoughts and reasoning are mostly in metal ; therefore the student should be so familiar with wood work before he begins on patterns, that the wood working will not give him much concern. Considering then that the student has handled tools before and knows something about them, we will call attention only to the common mistakes found in all school shops.

io A High School Course

The The first tool that we use is the iron

Plane jack plane. Since the rough stock from which we make this exercise is only about i2y 2 " long we shall use the jack plane for smoothing and for truing the surfaces. If we had to plane very long pieces we should use a fore plane; but since none of our work is very long, the individual kits need not contain a fore plane. A pattern maker has not mUch use for a smooth plane; because it is seldom that he wishes simply to smooth a piece without truing it.

The best thing to do first, is to remove the bit from the plane, examine the parts, see how they work, and learn to put the bit back in place and lock the cap. Do this enough times so that you lose all fear of doing it and will not hesitate to do it, in the future, when the bit needs sharpening. Under the direction of the teacher learn to do it gracefully. This can best be accomplished by holding the plane with the bottom flat in the left hand and drawing the cap-cam up with the right. Do not let it snap as it may break off. To avoid a common mistake in replacing the bit, hold the plane on a level with the eye and see that the bit lies flat upon the frog. In order for the bit to lie flat, the little finger which forms one end of the "Y" adjustment, must penetrate the square hole in the plane-iron cap and the little disc on the lateral lever must engage the slot in the plane-iron. If you are careful about this, the cap-cam will go down easily.

ii

Fig. I

In using the plane, most boys allow the rear of the plane to droop downward before the shaving begins (Fig. i), and when the plane has gone nearly the full length of the piece, and the knob is just passing the far end, they allow the front end to droop. This procedure will cause a hump or a hill to be planed on your piece. You can never plane a piece true, until you have learned always to keep the bottom of your plane parallel with your piece as it lies flat upon the bench (Fig. 2).

Fig.

Do not put the piece in the vise. If you push your plane straight to the bench-stop the piece will not dance around. The objection to putting the piece in the vise is that too much time is lost opening and closing the vise to test the piece. You cannot afford to lose time in this course. Modern times demand efficiency from the workers ; so we may as well begin, right now, to omit unnecessary motions.

Before planing, always run your finger lightly over the corners of your bit. If one corner projects farther than the other, change it by shifting the lateral lever. Never take a deep bite.

Sharpening The most disliked and at the the Bit same time the most necessary op-

eration in wood working is sharpening the tools. Too much stress cannot be laid on the importance of keeping the edge of the tools keen. Every boy should be provided with an oilstone which is kept perfectly flat. In whetting a tool on an oil stone, try to maintain the bevel which is ground on the tool, raising the handle only enough to cause the edge to grind on the stone. Notice that one side of a paring tool is always Hat. Keep this side Hat on the stone and NEVER raise the handle or you will ruin the effectiveness of the tool. (Fig. 3.)

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Fig. 3

One lesson from the teacher, if he gives you personal attention, will prove that in a very few minutes, you can sharpen a tool, so that you could shave yourself with it ; and this accomplishment will make you so happy that you will never again try to work with a dull tool.

Try- The next tool we use is a try-square.

Square It consists of a blade and a beam. Always hold the square loosely in the right hand, grasping the beam at its mid point (Fig. 4), and, when squaring an edge or end, see that you press the beam firmly against the Face Side or Face Edge, allowing the blade to touch lightly the surface being tested.

Pig- 5

Fig. 4

Fig. 6

Gage

The gage is an instrument that boys have difficulty in using. The great mistake is that they dig the spur into the wood so deeply that the head will not slide freely along the Face Side or Face Edge. (Fig. 5). To avoid this, tilt the head over until the corner of the beam bears on the edge that you are marking and the pressure rides mostly on this corner, leaving only enough pressure on the spur to make a fine light hair line. (Fig. 6.)

Scribe ' No pencil line is sufficiently accurate for this course and its use cannot be permitted. All laying off must be done with a scribe or knife, which must be sharp. The line must be deep and clean cut. It must be a hair line and we must work so accurately that by the expression "Working to a line" we mean splitting this hair line. These lines not only serve as a guide but also when planing off an end, prevent the little slivers from breaking out beyond the line and make a clean cut, square corner. Lay out everything with a knife accurately; then split the line and your work will be done correctly in one-fourth the time taken by the man who is too lazy to lay out the work, but takes off a shaving and then measures or tries the square and then takes another shaving, etc. This "cut and try" method does not make for efficiency.

Back The chief difficulty in using this tool is Saw to get the cut started. It is a mistake to put the teeth flat on the piece and try to start the kerf parallel with the line. You must start the kerf on the far corner. Hold the piece tightly against the bench hook with the left hand and then, without exerting pressure on the saw, draw the teeth across the corner at an angle to the surfaces, gradually lowering the handle as the kerf progresses, until the kerf is parallel to the line. (Fig. 7.) In these exercises you must never let the saw touch the line, but go very close to the line leaving only enough so that you can pare off a slight shaving with a plane or chisel.

Fig. 7

Block This little plane is used for planing end Plane grain on small blocks. Right here you should learn that, in order to cut wood smoothly, the tool must be given a lateral or sidewise movement, as well as a forward movement, otherwise you would squeeze the wood off, not cut it. To make this plain, imagine yourself cutting fresh bread. In this case you draw the knife toward you as well as press it down. This Drawing Cut will be insisted upon in all block plane and chisel work, where the wood fibers must be severed. This is not necessary in cutting "with the grain." The block plane should be held almost wholly within the right hand and the bit allowed to pass across the work at 45 ° to the edges and be drawn across the grain at the same time that it is pushed forward. The result should be a polished surface.

Bevel This is like a square with an adjustable blade, so that, with it we may draw lines at other angles than 90 .

Chisel It is foolhardy to attempt to use any but the keenest edged chisel on this work. You now know how to sharpen a plane bit. A chisel is much easier to sharpen. The same caution for whetting applies here : "Keep the back flat."

Two other necessary precautions are : "Use the drawing cut," and "Keep the brake on." By the latter is meant that you must keep your left hand rigidly braced against the job and allow the tool to slide between the thumb and forefinger, being ready at any time that the tool threatens to slip, to clamp the fingers together tightly and arrest the tool, before it slips out and splits away some of the wood that you didn't intend it should touch.

In modern industrial management it has been found of advantage to issue instruction cards to mechanics, outlining in their proper sequence the operations which shall be performed on each piece of work. If this is an advantage to an experienced mechanic certainly it is of far more help to the inexperienced one. Below is an outline of operations for making the first exercise.

INSTRUCTION CARD

Exercise in Working to Scribe and Gage Lines with Saw and Chisel

1 . Saw out a piece of rough white pine about 1" X 2 J A" X 12^".

2. True the Face Side with a jack plane and mark it. (To test the first side ; hold it up to the light parallel with the line of sight. If one corner appears high, plane it off and then test all over with the back of the square blade.)

3 . True the Face Edge and mark it. (This must be squared with the face side. Hold the square as explained under "Square.")

4. Plane the second side parallel to the Face Side. (Use gage lines to lay off the thickness.)

5. Lay off one end with knife and square. Saw off very near to line and plane to line with a block plane. (Always clamp beam of square tightly to either Face Side or Face Edge, no other. Line must run all around the piece.)

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6. Lay off the length and plane the other end.

7. Plane off the second edge parallel to the Face Edge. (Using gage lines to get the width.)

8. Measure along one edge and point off location of the lines for the gains. (Hold rule firmly against job, the divisions on the rule meeting the corner you wish to mark. Do not move rule each time you make a mark.)

9. Draw the outlines of the gains. (Use the following tools : bevel, knife, square, and gage.)

10. Saw just inside the knife lines in each gain, leaving very little to chisel off.

11. Chisel out the bottoms of the gains with a i-inch chisel. (Use the drawing cut.)

12. Chisel off the sides of the gains. (Use the drawing cut.)

13. Stamp your name and section on end of piece with steel letters. (Stamp name on end grain on every exercise.)

While the student is spending his shop periods making this exercise he should be spending his recitation periods acquiring a theoretic knowledge of the metal trades so that he can grasp the meaning of pattern making before he attempts to make his patterns.

Chapter IV. Moulding

Moulding is of such importance to the student of pattern making that it is well to give him an insight into it, at the outset. If there is no foundry connected with the school, at least one moulding bench should be equipped and maintained for demonstration purposes.

The purpose of these pages on moulding is not to give a complete course in moulding, but to give enough data so that by following the directions here given enough moulding can be done to demonstrate and make clear in the mind of the student just what happens to a pattern after it leaves the pattern shop ; to impress him with the importance of designing his pattern to suit the needs of the moulder.

A mould in connection with the foundry business, is a shaped opening in the sand into which hot metal is poured in order to produce a casting. There are three classes of moulding: i . Loam moulding.

2 . Dry sand moulding.

3. Green sand moulding.

Loam moulds are used for casting very heavy, plain pieces ; for example, a large, cylindrical drum for hoisting. The loam is a mixture of old moulding sand and chopped straw, which, when properly dampened, makes a plaster-like mass. This is plastered on a circular brickwork support, built to the approximate diameter, upon a large iron plate. A sweep is revolved on a spindle erected at the center. This will sweep a smooth round layer of loam on the inside of the circular brickwork. The surface is now dried and the whole thing lowered into a pit and packed around with sand to strengthen it, so that the weight of the metal will not burst out the side. The smooth surface will form the face of the drum. The hub and arms may be made in dry sand forms. It will be noticed that no large pattern is used in making this mould ; but the pattern maker must be familiar with it, because he will be called upon to make the sweeps, or skeleton patterns, which may be required.

Dry sand moulds are used for casting heavy work having considerable detail. A good example of this is a large steam engine cylinder, with its flanges, steam chest, exhaust outlet, etc. This mould is made in the same way as the green sand mould, which will be described in detail later ; but is thoroughly dried in an oven before pouring. The hot metalflowing in, causes less steam than in a green sand mould, and the hard caked mould offers more resistance to the heavy metal.

Green sand moulds, by far the most frequently used, are used for making medium and small castings. The material used for making a mould is called moulding scmd and is found in nature. It is found at various places in the United States and brings a good price. It is a combination of sand and clay. The sand component serves as the heat resisting element and its open grain keeps the mould porous, so that the steam and gases may find their way to the vent holes. The clay component serves to bind the particles of sand together so that the mould may be made to retain its form. Obviously clay alone could not be used, as the heat of the metal would bake the clay around the casting, like a brick. The sand causes the dried matrix to crumble easily, so that the casting may be removed.

There are two branches of green sand moulding: bench moulding and floor moulding.

Moulds for machine parts, such as a lathe bed, lathe leg, bandsaw frame, etc., are made in large flasks on the floor. Small things, like water faucets, small pipe joints, etc., are moulded in small flasks, on a bench, for convenience in handling.

We shall confine our attention to bench moulding; as it will serve to illustrate the principles of moulding which the student of this course must know.

Tools Used in Moulding

i. Flask: an open wooden or iron frame, in two or more sections, into which the sand is packed to make the mould. (Fig. 9.)

Fig. p. Flask

2. Cope : the upper half of the flask when in position for moulding.

3. Drag: the lower half.

4. Cheek: the intermediate portion when the flask consists of more than two parts.

5. Mould board : a flat board on which the pattern and drag are placed for ramming up. (Fig. 17.)

6. Bottom board : similar to mould board, on which the flask rests after rolling over. (Fig. 18.)