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A Manual Training Forge Shop

FORGE WORK

BY
WILLIAM L. ILGEN
FORGING INSTRUCTOR, CRANE TECHNICAL HIGH SCHOOL
CHICAGO, ILLINOIS

WITH EDITORIAL REVISION BY
CHARLES F. MOORE
HEAD OF MECHANICAL DEPARTMENT, CENTRAL HIGH SCHOOL, NEWARK, NEW JERSEY

NEW YORK CINCINNATI CHICAGO
AMERICAN BOOK COMPANY

Copyright, 1912, by
WILLIAM L. ILGEN.
FORGE WORK.
W. P. I

PREFACE

Teachers of forge work generally supply their own course of instruction and arrange the exercises for practice. The necessary explanations and information are given orally, and hence often with very unsatisfactory results, as the average student is not able to retain all the essential points of the course. It was the desire to put this instruction in some permanent form for the use of forge students that led the author to undertake this work.

The author wishes to express his thanks for the advice and encouragement of his fellow-teachers, Dr. H. C. Peterson, Mr. Frank A. Fucik, and Mr. Richard Hartenberg. Special obligations are due to Mr. Charles F. Moore, Head of the Mechanical Department in the Central Commercial and Manual Training High School of Newark, New Jersey, for his valuable editorial service.

Figures 146, 147, 150, 153, 157, and 158 have been reproduced, by permission of the publishers, from “Manufacture of Iron” and “Manufacture of Steel,” copyrighted 1902, by the International Textbook Company. Acknowledgments are due also to the Inland Steel Company for the privilege of using Figures 145, 148, 149, 159-163, 166; and to the Columbia Tool Steel Company for the use of Figures 151, 152, 154-156.

WILLIAM L. ILGEN.

[TABLE OF CONTENTS]

DEDICATED
TO THE MEMORY OF
MR. DAVID GORRIE

Fig. 1.—The Forge.

FORGE WORK

CHAPTER I
Tools and Appliances

1. The Forge.—The forge is an open hearth or fireplace used by the blacksmith for heating his metals. The kind most commonly used by the general smiths is such as can be seen in small villages or where the ordinary class of blacksmithing is done. (See [Fig. 1].)

Forges are usually built of brick; in form they are square or rectangular, and generally extend out from a side wall of the shop. The chimney is built up from the middle of the left side and is provided with a hood B, which projects over the fire sufficiently to catch the smoke and convey it to the flue.

The fire is kindled on the hearth A under the hood and over the tuyère iron. This iron, the terminal of the blast pipe that leads from the bellows E, is made in various forms and of cast iron; sometimes it has a large opening at the bottom, but often it has none.

The bellows are operated by the lever F, which expands the sides and forces air through the tuyère iron, thereby causing the fire to burn freely and creating a temperature sufficient for heating the metals.

The coal box C is to the right, where it is convenient. The coal should always be dampened with water to prevent the fire from spreading. This will produce a more intense and more concentrated heat, so that a certain part of the metal can be heated without danger of affecting the rest.

Fig. 2.—A Manual Training Forge.

The water tub, or slack tub D, as it is more properly called, stands at the right of the forge near the coal box, where the water for dampening the coal can be most readily obtained. It is used for cooling the iron or tongs and for tempering tools.

Modern forges are made of cast iron or sheet steel. There are various kinds designed mostly for special purposes. They are generally used with the fan blast instead of the bellows and have a suction fan for withdrawing the smoke.

The forge illustrated in [Fig. 2] was designed for manual training use and is excellent for such a purpose. The bottom or base has six drawers which provide convenient places for keeping exercises and individual tools. As each drawer is provided with a special lock, much of the trouble resulting from having the tools or the work mislaid or lost is prevented.

Fig. 3.—Sectional View of the Forge shown in [Fig. 2].

The hearth A where the fire is built is provided with a cast-iron fire pot or tuyère. This is constructed with an opening at the bottom where there is a triangular tumbler which is cast upon a rod projecting through the front of the forge; by revolving the rod and tumbler the cinders or ashes can be dropped into the ash drawer at the bottom of the forge without disturbing the fire. A sectional view of these parts is shown in [Fig. 3], also the valve which regulates the blast.

Suspended on the upper edge surrounding the hearth, and located to the right and left of the operator, two boxes C and D are located, which are used for storing an adequate supply of coal and water, where they may be conveniently obtained.

In front are two handles; the upper one operates the clinker or ash valve, the lower one regulates the blast.

The front and back edges surrounding the hearth are cut out, so that long pieces of metal can be laid down in the fire. These openings can be closed, when desired, with the hinged slides shown at G.

The hood B projects over the fire sufficiently to catch the smoke and convey it to the opening of the down-draft pipe E. When necessary the hood can be raised out of the way with the lever F, which is constructed with cogs and provided with a locking pin to keep the hood in position.

2. Fire Tools.—The necessary tools required for maintaining the fire and keeping it in good working condition are shown in [Fig. 4]. A is the poker with which the coke can be broken loose from the sides. B is the rake with which the coke can be moved over the fire on top of the metal to prevent the air from retarding the heating. The shovel C is used for adding fresh coal, which should always be placed around the fire and not on top. In this way unnecessary smoke will be prevented, and the coal will slowly form into coke. The dipper D is used for cooling parts of the work that cannot be cooled in the water box. The sprinkler E is used for applying water to the coal, or around the fire to prevent its spreading.

Fig. 4.—Fire Tools.
A, poker; B, rake; C, shovel; D, dipper; E, sprinkler.

3. Fuels.—The fuels used for blacksmithing are coal, coke, and charcoal. Most commonly a bituminous coal of superior quality is used. It should be free from sulphur and phosphorus, because the metals will absorb a certain amount of these impurities if they are in the fuel. The best grade of bituminous coal has a very glossy appearance when broken.

Coke is used mostly in furnaces or when heavy pieces of metal are to be heated. It is a solid fuel made by subjecting bituminous coal to heat in an oven until the gases are all driven out.

Charcoal is the best fuel, because it is almost free from impurities. The most satisfactory charcoal for forging purposes is made from maple or other hard woods. It is a very desirable fuel for heating carbon steel, because it has a tendency to impart carbon instead of withdrawing it as the other fuels do to a small extent. It is the most expensive fuel, and on that account, and because the heating progresses much more slowly, it is not used so generally as it should be for heating carbon steel.

4. The Anvil.—The anvil ([Fig. 5]) is indispensable to the smith, for upon it the various shapes and forms of metal can be forged or bent by the skilled workman. Except for a few that have been designed for special purposes, it has a peculiar shape which has remained unchanged for hundreds of years. That the ancient smiths should have designed one to meet all requirements is interesting to note, especially as most other tools have undergone extensive improvements.

Anvils are made of wrought iron or a special quality of cast iron. In the latter case the face is sometimes chilled to harden it, or is made of steel which is secured to the base when the anvil is cast. Those that are made of wrought iron are composed of three pieces: the first is the base B which is forged to the required dimensions; the second is the top which includes the horn C and the heel; the third is the face A of tool steel which is welded to the top at the place shown by the upper broken line. The top and base are then welded together at the lower broken line.

Fig. 5.—The Anvil.

After the anvil has been finished, the face is hardened with a constant flow of water, then it is ground true and smooth and perfectly straight lengthwise, but slightly convex crosswise, and both edges for about four inches toward the horn are ground to a quarter round, thus providing a convenient place for bending right angles. This round edge prevents galling, which is liable to occur in material bent over a perfectly square corner.

The round hole in the face is called the pritchel hole, over which small holes can be punched in the material. When larger ones are to be punched, they can be made on a nut or collar placed over the square hole or hardy hole. This hardy hole is used mostly for holding all bottom tools, which are made with a square shank fitted loosely to prevent their becoming lodged.

The flat portion D at the base of the horn, and a little below the level of the face, is not steel, consequently not hardened, and is therefore a suitable place for cutting or splitting, because there is not much liability of injuring the cutter if the latter comes in contact with the anvil.

The horn C is drawn to a point and provides a suitable place for bending and forming, also for welding rings, links, or bands.

The anvil is usually mounted on a wooden block and is securely held by bands of iron as shown in the illustration, or it may be fastened by iron pins driven around the concave sides of the base. It is sometimes mounted on a cast-iron base made with a projecting flange which holds the anvil in place.

A convenient height for the mounting is with the top of the face just high enough to touch the finger joints of the clenched hand when one stands erect. It is generally tipped forward slightly, but the angle depends considerably upon the opinion of the workman who arranges it in position.

For some time most of the anvils were made in Europe, but at present the majority that are purchased here are made by American manufacturers.

5. The Hammers.—Of the multitude of tools used by mechanics, the hammer is undoubtedly the most important one. There was a time when man had only his hands to work with, and from them he must have received his ideas for tools. Three prominent ones which are used extensively at present were most probably imitations of the human hand. From the act of grasping, man could easily have originated the vise or tongs for holding materials that he could not hold with the hand. Scratching with the finger nails undoubtedly impressed him with the need of something that would be effective on hard substances, and so he devised such tools as picks, chisels, and numerous other cutting instruments.

The clenched fist must have suggested the need of a hammer. The first thing to be substituted for the fist was a stone held in the hand. Next a thong of fiber or leather was wound around the stone, and used as a handle. From these beginnings we have progressed until we have hammers of all sizes and shapes, from the tiny hammer of the jeweler to the ponderous sledge. Workmen have adapted various shapes of hammers to their individual needs.

Fig. 6.—Hand Hammers.
A, ball peen hammer; B, cross peen hammer; C, straight peen hammer.

6. The ball peen hammer (A, [Fig. 6]), sometimes called a machinist’s hammer, is very conveniently shaped for forging, as the ball end is handy for drawing out points of scarfs or smoothing concave surfaces. A suitable weight of this kind of hammer is one and a half pounds, but lighter ones can be used to good advantage for fastening small rivets.

7. The cross peen hammer (B, [Fig. 6]) is one of the older styles and is mostly employed in rough, heavy work or for spreading metal.

8. The straight peen hammer (C, [Fig. 6]) is shaped similarly to the ball peen hammer, except that the peen is flattened straight with the eye. It is convenient for drawing metal lengthwise rapidly.

9. The sledges (A, B, and C, [Fig. 7]) are used for striking on cutters, swages, fullers, or other top tools; when they are used by the helper, the blacksmith can be assisted in rapidly drawing out metal. The only difference between these two sledges is in the peen—one is crosswise with the eye and the other lengthwise. The double-faced sledge C is sometimes called a swing sledge, because it is used mostly for a full swing blow.

Fig. 7.—The Sledges.

10. The Tongs.—There is an old saying that “a good mechanic can do good work with poor tools,” which may be true; but every mechanic surely should have good tools, on which he can rely and thereby have more confidence in himself. Among the good tools that are essential for acceptable smith work are the tongs.

Very few shops have a sufficient variety of tongs to meet all requirements, and it is often necessary to fit a pair to the work to be handled. Sometimes quite serious accidents happen because the tongs are not properly fitted. They should always hold the iron securely and, if necessary, a link should be slipped over the handles as shown in B, [Fig. 8]. The workman is thus relieved from gripping the tongs tightly and is allowed considerable freedom in handling his work.

11. The flat-jawed tongs are shown at A, [Fig. 8]. They are made in various sizes to hold different thicknesses of material. Tongs of this kind hold the work more securely if there is a groove lengthwise on the inside of the jaw; the full length of the jaw always should grip the iron.

Fig. 8.—The Tongs.
A, flat-jawed tongs; B, hollow bit tongs; C, pick-up tongs; D, side tongs; E, chisel tongs; F, link tongs; G, tool or box tongs.

12. The hollow bit tongs, shown at B, [Fig. 8], are very handy for holding round iron or octagonal steel. They can be used also for holding square material, in which case the depressions in the jaws should be V-shaped.

13. The pick-up tongs (C, [Fig. 8]) are useful for picking up large or small pieces, as the points of the jaws are fitted closely together, and the two circular openings back of the point will securely grip larger pieces when seized from the side.

14. The side tongs (D, [Fig. 8]) are used for holding flat iron from the side. Tongs for holding round iron from the side can be made in this form with circular jaws.

15. The chisel tongs are shown at E, [Fig. 8]. One or more pairs of these are necessary in all forge shops. As the hot and cold cutters frequently get dull or broken, it will be necessary to draw them out and retemper them; and, as the heads of these cutters become battered considerably, they are difficult to hold without chisel tongs. The two projecting lugs at the ends of the jaws fit into the eye, and the circular bows back of them surround the battered head of the cutter, so that it can be held without any difficulty.

16. The link tongs (F, [Fig. 8]) are as essential as anything else required in making chains or rings of round material. They can be made to fit any size of stock.

17. The tool or box tongs (G, [Fig. 8]) should be made to fit the various sizes of lathe tool stock that are used. They should be made substantially and fit the steel perfectly so that it can be held securely and without danger of stinging the hand, while the tool is being forged. Another style of tool tongs is made with one jaw perfectly flat; on the other jaw, lugs are provided to hold the steel firmly. These are not illustrated.

Almost an unlimited number of different tongs could be explained and illustrated, but, from those given, any one should be able to add to or change the tongs he has so that his material can be securely held.

18. Anvil and Forging Tools.—If a complete set of these tools were to be illustrated and explained, a volume would be required. Even then, the worker would very often be compelled to devise some new tool to suit the particular work at hand. One advantage that the blacksmith has over all other mechanics is that when a special tool is required, if he is a thorough mechanic he can make it.

An almost unlimited number of tools might be required in a general smith shop; but only such tools as are essential in manual training or elementary smith work will be considered here.

Fig. 9.
A, hardy; B, cold cutter; C, hot cutter.

19. The hardy (A, [Fig. 9]) should fit the hardy hole of the anvil loosely enough so that it will not stick or wedge fast. It is made of cast steel and should be tempered so that it will not chip or batter from severe use. It is an indispensable tool, especially to one who has to work without a helper, for with it iron can be cut either hot or cold, and steel when it is heated. The material should be held on the cutting edge of the hardy, then struck with the hammer. A deep cut should be made entirely around the material, round, square, or flat, so that it can be broken off by being held over the outer edge of the anvil and struck a few downward blows with the hammer.

Material should not be cut through from one side, for the cut would then be angular instead of square; furthermore, there would be the effect of dulling the hardy if the hammer should come in contact with it. The hardy is frequently used to mark iron where it is to be bent or forged, but it is not advisable to use it for such purposes, unless the subsequent operations would entirely remove the marks, for they might be made deep enough to weaken the metal, especially at a bending point.

20. The cold and hot cutters (B and C, [Fig. 9]) are made, as are all other top tools, with an eye for inserting a handle, and should be held by the workman while some one acting as his helper strikes on them with the sledge. The handles can be of any convenient length from eighteen inches to two feet. Cast steel should be used for making both these cutters, but their shapes differ somewhat. The cold cutter B is forged considerably heavier on the cutting end than is the hot cutter, in order to give it plenty of backing to withstand the heavy blows that it receives. The cutting edge is ground convex to prevent the possibility of the corners breaking off easily, and is ground more blunt than the hot cutter. It should be used only to nick the metal, which should then be broken off with the hammer or sledge, as described in cutting iron with the hardy.

21. The hot cutter (C, [Fig. 9]) is drawn down, tapering from two depressions or shoulders near the eye to an edge about ¹⁄₈ inch thick, which is ground equally from both sides to form a cutting edge parallel with the eye. It should be used exclusively for cutting hot metal, because the shape and temper will not stand the cutting of cold iron. In order to avoid dulling the cutter and the possibility of injuring some one with the piece of hot metal that is being cut off, the cut should be held over the outside edge of the anvil when the final blows are being struck; the operation will then have a shearing action, and the piece of metal will drop downward instead of flying upward.

Great care should be taken in hardening and tempering each of these cutters to prevent possible injury from small particles of steel that might fly from them if they were tempered too hard. The cold cutter should be hard enough to cut steel or iron without being broken or battered on its cutting edge. The hot cutter should not be quite so hard and should be dipped in water frequently when it is being used to prevent the temper from being drawn.

22. The flatter (A, [Fig. 10]) is as useful and as essential for the production of smooth and nicely finished work as the finishing coat of varnish on a beautiful piece of furniture. Any work that is worth doing is certainly worth doing well, and in order to make forge work present a finished appearance the smith should use the flatter freely. With it the rough markings of the various forging tools or hammer can be entirely removed. By using it while the work is at a dull red heat, and by occasionally dipping the flatter in water before it is applied, all the rough scale can be removed, thus leaving the work with a smooth, finished appearance.

There are various sizes of this tool, but one with a 2-inch face is convenient for use on light forgings. The edges of the face may be made slightly round, so that markings will not be left on the work, but frequently the edges are left perfectly square.

Fig. 10.
A, flatter; B, square-edged set hammer; C, round-edged set hammer.

It is not necessary to temper this tool; in fact, the constant hammering on it has a tendency to crystallize the steel, often causing it to break off at the eye. As the constant hammering on the head of the flatter will also cause the head to become battered, it is good practice frequently to draw out the head and lay the flatter aside to cool. This will anneal the steel and prevent crystallization, at least for some time.

23. The square-and round-edged set hammers (B and C, [Fig. 10]) are employed for various purposes. The former is used for making square shoulders or depressions such as could not be produced with the hand hammer alone, or for drawing metal between two shoulders or projections. The latter is used for the same purposes, with the exception that it produces a rounded fillet instead of a square corner. It is also convenient for use in small places where the flatter cannot be employed.

The sizes of these tools vary according to the requirements of the work, but it is advisable to have about three sizes of the square-edged one. A good outfit of set hammers consists of one ⁵⁄₈-inch, one ³⁄₄-inch, one 1-inch, all square-edged; and one round-edged set with a 1¹⁄₄-inch face. These four should fulfill all requirements for light forgings. These tools need not be tempered, for the reason explained in connection with the flatter.

24. The punches (A, B, and C, [Fig. 11]) are merely samples of the multitude of such tools that may be required. They may be of various sizes, depending upon the requirements of the work, and either round, square, or oval in shape at the end. The hand punch A is held with one hand while blows are delivered with the other. It is convenient for punching holes in light pieces; but when the work is heavy the intense heat from the metal makes it impossible to hold a punch of this kind.

Fig. 11.—The Punches.

In such cases the handle punches B and C are employed. They eliminate the danger of burning the hand, but it is necessary to have some one act as helper and do the striking. The proper way to use a punch on hot metal is to drive it partly through, or until an impression can be seen on the opposite side after the punch has been removed; then the punch is placed on the impression and driven through the metal while it is held over the pritchel hole, the hardy hole, or anything that will allow the punch to project through without causing the end to be battered. If heavy pieces of metal are to be punched, it is a great advantage to withdraw the tool, drop a small piece of coal into the hole, and cool the punch before again inserting it. The coal prevents the tool from sticking fast, and the operation can be repeated as often as necessary.

Punches need not be tempered, because the strength of the steel from which they should be made will withstand the force of the blows, and also because the metal is generally hot when the punches are used; therefore the temper would be quickly drawn out of them. If sheet metal or light material is to be punched cold, it is advisable to harden the punch slightly; then the hole may be punched through from one side, while the metal is held on something containing a hole slightly larger than the punch. This method has the effect of producing a smoothly cut hole, provided the metal is properly placed.

Fig. 12.—The Top and Bottom Swages.

25. The top and bottom swages ([Fig. 12]) are made with semicircular grooves of different sizes to fit the various diameters of round material. The former has an eye for the insertion of a handle by which it is held when in use. The eye should be crosswise to the groove in the face. The bottom swage is made with a square projecting shank to fit loosely into the hardy hole of the anvil. It should be placed in position for use with the groove crosswise to the length of the anvil, unless the form of the forging should require otherwise. Swages are conveniently used for smoothing round material after it has been welded, or for swaging parts of a forging after they have been roughly hammered out. By dipping the top swage in water occasionally while in use, the work can be made much smoother and the scale of oxide removed; this is called water swaging.

Fig. 13.—The Top and Bottom Fullers.

26. The top and bottom fullers ([Fig. 13]) are made in pairs with convex semicircular projections or working faces, whose diameters should correspond, if intended to be used together. As the former is quite frequently used alone, it may be made of any desired size. The top fuller, like the top swage, is made to be used with a handle; the bottom fuller, fitted to the anvil like a bottom swage, generally is placed for use with the length of its face parallel to the length of the anvil.

They are used together for forming depressions or shoulders on opposite sides of the material; from the shoulders thus formed, the metal may be forged without disturbing them. They are used also for rapidly drawing out metal between shoulders or projections which may have been previously made and are to be left undisturbed. The top fuller is used singly in making scarfs for welding, in forming grooves, in smoothing fillets and semicircular depressions, or in forming shoulders on only one side of metal.

27. The button head set or snap (A, [Fig. 14]) as it is sometimes called, has a hemispherical depression on its face. It is used for making heads of rivets or finishing the heads of bolts. Only a few different sizes are required, unless considerable riveting or bolt making is to be done.

Fig. 14.
A, the button head set; B, the heading tool.

28. The heading tool (B, [Fig. 14]) is used exclusively for forming the heads of bolts or rivets. Formerly a very large assortment of these tools was required in a general shop; but as bolts can now be made so cheaply by modern machinery, there are not many made by hand. It would be advisable to have a few general sizes, however, because they are sometimes convenient in making other forgings, and bolt making affords an instructive exercise.

29. The swage block (A, [Fig. 15]) rests on a cast-iron base B. It is a very useful tool in any smith shop and does away with the necessity of having a large assortment of bottom swages, as only top swages will be required for large-sized material. The block is made of cast iron and of different thicknesses. The depressions on the edges include a graduated series of semicircular grooves that can be used in place of bottom swages; a large segment of a circle, which is handy in bending hoops or bands; graduated grooves for forming hexagonal boltheads or nuts; and sometimes a V-shaped and a right-angled space used for forming forgings.

Fig. 15.—The Swage Block.

The holes through the blocks are round, square, or oblong. The round ones can be used in place of heading tools for large sized bolts, or in breaking off octagon or round steel after it has been nicked with the cold cutter. The square holes may be used either for making and shaping the face of a flatter or a round-edged set hammer, or in place of a heading tool, when a square shoulder is required under the head. They may be used, also, for breaking square steel. The oblong holes are convenient for breaking lathe tool material. Some swage blocks have in addition a hemispherical depression on the side, convenient for forming dippers or melting ladles.

The base upon which the swage block rests is constructed with lugs on the inner side, as indicated by the broken lines on the sketch. Upon these it is supported, either flat or on any of its four edges. These lugs prevent the swage block from tipping sidewise.

30. The surface plate (C, [Fig. 16]) is generally made of cast iron about 1¹⁄₂ to 2 inches thick, from 20 to 24 inches wide, and from 3 to 4 feet long. It should be planed perfectly smooth and straight on its face, the edges slightly round. It should be supported on a strong wooden bench D and placed somewhere in the middle of the shop so that it is accessible to all the workmen. On it work is tested to see whether it is straight, perpendicular, or if projections are parallel. The anvil is sometimes used for this purpose, but as it is subjected to such severe use, the face becomes untrue and therefore cannot be depended upon. A true surface plate is always reliable and convenient for testing work.

Fig. 16.—The Surface Plate.

31. The tapered mandrels ([Fig. 17]) are made of cast iron, and are used for truing rings, hoops, bands, or anything that is supposed to have a perfectly circular form. The height ranges from 2¹⁄₂ to 5 feet; the largest diameter varies from 8 to 18 inches. They are cone-shaped with a smooth surface, and should be used with caution. The blows should be delivered on the metal where it does not come in contact with the mandrel; when bands of flat material are to be trued, the best method is to place them on the mandrel from each side alternately. Unless this precaution is observed, the band will be found tapered the same as the mandrel. Alternating is not so necessary when bands or rings of round material are handled.

Mandrels are sometimes made in two sections, as shown at B and C. As B is made to fit into the top of C, the two parts become continuous; the smaller one can also be held in the vise or swage block and thus used separately. They are frequently made with a groove running lengthwise, which allows work to be held with tongs and provides a recess for any eyebolt or chain that may be attached to the ring.

Fig. 17.—The Tapered Mandrels.

It should not be supposed that all mandrels are of this particular form; any shape of bar, block, or rod of iron that is used for the purpose of forming or welding a special shape is called a mandrel.

32. Bench and Measuring Tools.—Another set of blacksmith appliances includes the bench vise, chisels, center punch, rule, dividers, calipers, scriber, square, bevel, hack saw, and files.

Fig. 18.—The Bench Vise.

33. The bench or box vise ([Fig. 18]) is not ordinarily used in general blacksmithing. The back jaw of a general smith’s vise extends to the floor, forming a leg, and is held in position on the floor by a gudgeon on its end. This vise is not illustrated, because the bench or box vise is preferable for manual training work.

The vise should be set so that the tops of the jaws are at the height of the elbows,—a position convenient in filing. It is used for holding the work for filing, chipping, twisting, and sometimes for bending. But when it is used for bending, especially when bending a right angle, the operation should be performed cautiously, for the sharp edges of the jaws are very liable to cut the inner corner of the angle and cause a gall which will weaken the metal at the bend.

34. The chisels (A and B, [Fig. 19]) are very familiar, yet, though they are so common, they are the most abused tools used by both skilled and unskilled workmen. The mere name “cold chisel” seems to convey the impression to most people that with it they ought to be able to cut anything. But that impression is wrong; chisels ought to be made of a certain grade of steel and drawn for either rough or smooth work, as may be required. Then they should be properly tempered to cut the material for which they are intended.

A chisel for rough, heavy work should not be drawn too thin or too broad at the cutting edge. If it is flattened out into a fan-shaped cutting edge, there should be no surprise if it breaks, for, in order to make a chisel stand rough usage, it should have sufficient metal to back up the corners. On the other hand, a chisel for smooth finishing work can safely be drawn thin but not fan-shaped, as the cuts that ought to be required of such a chisel should not be heavy. A chisel for ordinary work ought to be ground so that the two faces form an angle of 60 degrees; if the work is heavy, it should be ground even more blunt.

Fig. 19.
A, cold chisel; B, cape chisel; C, center punch; D, rule.

The chisel illustrated at A represents a common cold chisel, which can be used for various purposes. The chisel B is called a cape chisel and is used for cutting and trimming narrow grooves and slots. It is indispensable for cutting key seats in shafting or work of that kind. On account of its being used in such narrow places it is necessary to make the cutting edge somewhat fan-shaped to prevent the chisel from sticking fast; but for additional strength the metal is allowed to spread, as shown. When using the cape chisel, it is a good practice occasionally to dip the cutting edge in some oily waste, which will tend to prevent its wearing away or sticking.

35. The center punch (C, [Fig. 19]) should be made of the same quality of material as the cold chisel. It can be made of steel from ¹⁄₄ to ⁵⁄₈ of an inch in diameter; octagon steel is preferable. After it has been roughly drawn out, it is ground to a smooth round point, then it is tempered as hard as it will stand without breaking. It is used for marking centers of holes to be drilled, or for marking metal where it is to be bent, twisted, or forged. When used for marking hot metal, it is frequently made with an eyehole in the body, so that a small handle can be inserted; this will prevent burning the hands.

36. The rule (D, [Fig. 19]) should be of good quality. The one best adapted for forge work is the 2-foot rule, which is jointed in the center. It is ³⁄₄ inch wide and is made of either tempered spring steel or hard rolled brass.

Fig. 20.
A, dividers; B, calipers; C, scriber; D, square; E, bevel.

37. The dividers (A, [Fig. 20]) are used for measuring distances and for describing circles. The points are clamped in a rigid position with the small thumbscrew, which comes in contact with the segmental arc. Close adjustments can be made with the milled-edge nut on the end of the segmental arc. When metal is to be bent to a circular form, a good method is to rub chalk on the surface plate and describe the desired curve on this chalk. As the markings thus made are not easily removed, this plan is much better than drawing upon a board.

38. The calipers (B, [Fig. 20]) are used for measuring diameters, widths, and thicknesses. Those illustrated are the kind generally used in forge work. They are called double calipers and are the most convenient because two dimensions can be determined by them. As the accuracy of the work depends on them, they should be well made. In the illustration here given, each bow is held securely by an individual rivet. Sometimes they are secured with one; if so, the rivet should be square in the straight central part and tightly fitted. The projecting ends of the rivet should be filed round, and the holes in the bowed sides should be made to fit the round ends of the rivet; then the sides should be riveted on tight so that each bow may be moved independently of the other.

39. The scriber or scratch awl (C, [Fig. 20]) is used in marking holes, sawing, chipping, or in laying out distances, which can afterward be marked with a center punch if required. It should be made of a good quality of steel, and the point should be well hardened so that it will cut through the surface scale of the metal. A suitable-sized steel for making a scriber is ³⁄₁₆ inch round and the length over all about 6 inches.

40. The square (D, [Fig. 20]) is another indispensable tool when accurate work is to be produced. Convenient sizes for manual training work are the 8 × 12-inch, with a 16 × 24-inch for general use.

41. The bevel (E, [Fig. 20]) should be used when bending and laying out angles of various degrees. When metal is to be bent to a given angle, the pupil should set and use the bevel.

42. The hack saw ([Fig. 21]) is at present considered a necessary part of any forge shop equipment. It is used for sawing iron or untempered steel, and when a power shear is not included in the equipment, considerable filing can be saved by sawing. The frame illustrated is adjustable so that the blades can be made of different lengths and be set at right angles to the frame, which is sometimes convenient.

When using the hack saw, make slow, full-swing strokes; when drawing back for another stroke, it will prolong the efficiency of the blades if the saw is raised up to prevent the teeth from bearing on the metal, as the backward stroke is more destructive to the teeth than the forward or cutting stroke. The blades are made from 8 to 12 inches in length, ¹⁄₂ inch in width, and with from 14 to 25 teeth to the inch. They are tempered so hard that they cannot be filed, but are so inexpensive that when they cease to be efficient they may be thrown away.

Fig. 21.—The Hack Saw and Files.

43. The files ([Fig. 21]) are illustrated merely to show that they are to be used for special purposes. As finishing or filing is almost a trade in itself, the file should not be used in blacksmithing, unless it is especially necessary. A piece of smith’s work that has been roughly forged is much more admirable than a highly polished piece that has been filed into elegance.

Files are round, flat, square, half round, and of numerous other shapes, and vary in lengths and cuts for rough or smooth filing. Any of them may be used as required, but it should be remembered that filing is not blacksmithing.

Questions for Review

What is the main difference between the old type of smithing forge and a modern one? How is the air supplied for each? What is a tuyère iron? Describe the hearth. What kind of coal is used for forging? Is coal the best fuel for heating all metals? Why is charcoal the best fuel for heating carbon steel? How should the fire be built to prevent making excess smoke? What other fuel is used in forging? What kind of work is it used for? Describe the different parts of the anvil. How is a cast-iron anvil hardened? How is a wrought-iron anvil hardened? Name and describe the different kinds of hammers. Why should the tongs fit properly the iron to be handled? Name and describe the different tongs you have been made familiar with. How would you secure the tongs to relieve the hand?

What is a hardy? What is it used for? Explain the proper method of using it. Is it always good practice to use a hardy for marking the iron? Why? What is the difference between a cold and a hot cutter? What is the general use for a flatter? Should it be tempered? Why? What are set hammers? What is a punch used for? Explain the difference between a hand punch and a handle punch. When punching a heavy piece of metal, how is the tool prevented from sticking fast? Are all punches tempered? Why? Describe and explain the use of top and bottom swages. How should the bottom swage be placed for use? What is meant by water swaging? State the effect it has on the iron. What are top and bottom fullers used for? Are they always used in pairs? How is the bottom one placed for use? What are the button head set and heading tool used for? What is the special advantage of having a swage block? Explain some of the different uses of that tool. What is the special use of the surface plate? What is the tapered mandrel used for? Are all mandrels of this particular kind? Explain others. Is it good practice to use the vise for bending? Why? Describe the cold chisel. Should all cold chisels be made alike? What is the center punch used for? Describe the other bench and measuring tools mentioned. What is the special objection to using the files?

CHAPTER II
Forging Operations

44. The Hammer Blows.—Metal can be forced into desired shapes or forms by delivering the hammer blows in different ways. All hammer blows are not alike; some will have one effect and others will produce an entirely different result.

45. The upright blow is delivered so that the hammer strikes the metal in an upright position and fully on the anvil. Such blows force the metal equally in all directions, providing the surrounding dimensions are equal. They will also reduce the thickness of the metal in the direction in which they are delivered, the reduction depending upon the amount of force put into the blows. They are used for drawing where the metal is supposed to spread equally in all directions and for making smooth surfaces.

Fig. 22.—The Upright Blow.

Figure [22] shows an upright blow as delivered on a piece of flat material. If the material is as wide as the face of the hammer, or wider, the force of the blow will spread the metal equally, but if it is narrower, the blow will lengthen the material more rapidly, because the hammer will cover more in length than in width.

46. The edge-to-edge blow is delivered so that the edge or side of the hammer face will be directly above the edge or side of the anvil. When blows are delivered in this manner (a, [Fig. 23]), the hammer forms a depression on the upper side of the metal and the anvil forms one on the bottom.

Fig. 23.—The Edge-to-edge Blow.

When a piece of metal is to be drawn to a smaller dimension, with shoulders opposite each other, on either two or four sides, these blows will produce the required result to the best advantage. They are more effective if the metal is held at a slight angle across the edge of the anvil face, but then the hammer blows must be delivered a little beyond the anvil edge, so that the upper and lower depressions in the metal will be formed exactly opposite each other, as shown at b, where the depressions are indicated by the broken lines.

In forming shoulders such as are required on the hasp exercise (page [64]) the first pair may be formed as shown at b and the second pair as shown at c. In the latter case the metal is held across the nearer edge of the anvil face and the blows delivered in a manner similar to that described in the preceding paragraph. Hammer blows of this class may be used on any edge of the anvil as required.

47. The overhanging blow is delivered so that half the width of the hammer face extends over the edge of the anvil. (See [Fig. 24].)

Fig. 24.—The Overhanging Blow.

It is used for forming shoulders on one side of the metal and for drawling out points of scarfs. When blows are delivered in this manner, the anvil will form a depression or shoulder on the lower side of the metal, and the hammer will keep the metal straight on the upper side.

This blow also will be more effective if the metal is held at a slight angle across the edge of the anvil face, but the blows must always be delivered squarely on the upper side of the metal to keep it straight.

48. The beveling or angle blows are delivered at any angle that the form of the work may require. When the metal is to be drawn with a taper on one side, it must be held level on the anvil and the blows delivered at an angle determined by the amount of taper required. Figure [25] shows the manner of holding the metal and the way the blows are to be delivered.

Fig. 25.—The Beveling or Angle Blow.

When the metal is to be drawn tapering on two opposite sides, it should be held to the proper angle on the anvil to establish the taper desired on the bottom, while the hammer blows are delivered so as to form a similar taper on the upper side. (See [Fig. 25].)

Fig. 26.—Drawing Metal to a Point by Beveling or Angle Blows.
A, correct position; B, incorrect position.

Fig. 27.—The Leverage Blow.

Blows of this kind are used for chamfering corners or edges, and may be delivered at any required angle. They are also used when drawing metal to a point, either square, round, hexagonal, or octagonal, but the metal should be held on the anvil, as shown at A, [Fig. 26]. Then the hammer will not come in contact with the face of the anvil, as shown at B. If the hammer strikes the anvil, small chips of steel are liable to break off from the hammer at the place indicated by c, and cause serious injury.

Fig. 28.—Bending by Leverage Blows.

49. The leverage blows are used mostly for bending, as they will not leave marks where the bending occurs. For instance, when a ring is to be formed, the metal is first held in the tongs and rested on the horn of the anvil, as shown in [Fig. 27]. Note that the metal will bend at a, providing the heat is uniform. If, therefore, bending is required at a certain place, that place should rest on the anvil and the blows should be delivered beyond it.

After the first end has been bent to the required radius, the other should be bent by holding it in the manner shown in [Fig. 28], because the joint of the tongs will prevent its being struck out of them while the blow is being delivered. When both ends have been bent to the proper radius, the ring should be finished as described in the ring exercise (page [74]), where upright blows are used with a leverage effect.

50. The backing-up blows are used to upset metal when it is impossible to upset it in the usual manner, and in backing up the heel of a scarf.

Fig. 29.—The Backing-up Blow, for Upsetting.

Upsetting with backing-up blows is done in the manner shown in [Fig. 29]. The metal should be extended over the anvil and thrust forward as the blow is being delivered, to get the best results. This will also prevent jarring the hand. The metal should be as hot as possible when being upset in this manner.

The heel of a scarf is formed with backing-up blows after the metal has been upset in the usual manner. The blows should be directed so that they will have an upsetting effect, as indicated in [Fig. 30], and not a drawing one. After a few blows have been delivered with the face of the hammer, they should then be delivered with the ball to form the heel better and more rapidly.

Fig. 30.—Backing-up Blows used for Scarfing.

51. The shearing blow (see [Fig. 31]) is conveniently used for cutting off small portions of metal instead of employing the hardy. It is delivered so that the side or edge of the hammer will pass by and nearly against the side or edge of the anvil. A blow so delivered will have a shearing effect and cut the metal. It is perfectly proper to use this blow for its intended purpose, but it should not be used when the edge-to-edge blow is the one really required.

52. Forging.—Forging is the operation of hammering or compressing metals into a desired shape. Seven specific operations are used. Sometimes a piece of work or forging requires two, three, or even all of them to complete it. These operations are designated by the following names: drawing, bending, upsetting, forming, straightening, twisting, and welding.

Fig. 31.—The Shearing Blow.

53. Drawing, the process of spreading or extending metal in a desired direction, is accomplished by hammering or by pressing the metal between such tools as the swages and fullers, or by holding it on the anvil and using either of the set hammers, the flatter, or the fuller. When using any of these pressing tools for drawing, a helper is supposed to use the sledge to deliver the blows upon them.

It is always best to draw round metal with the swages, as it will be smoother when finished than if it were done with the hammer; it should be rolled in the swage a little after each blow of the sledge, and after a complete revolution in one direction it should be turned in the opposite direction, and so alternately continued until finished. Especially if iron is being drawn, this will prevent twisting of the fiber, which, if prolonged, would cause the metal to crack. Figure [32] shows the method of drawing with the swages.

When drawing any shape or size of metal to a smaller round diameter, it is best first to draw it square to about the required size, delivering the blows by turns on all four sides, then to make it octagonal, and finally round. The finishing should be done with the swages, if those of proper size are at hand; if not, light blows should be used, and the metal revolved constantly in alternate directions, to make an acceptable shape.

Fig. 32.—Drawing with the Swages.

Fig. 33.—Drawing with the Flatter.

Drawing with the top and bottom fullers, in the manner shown with the swages ([Fig. 32]), ought to be done cautiously, as the metal decreases in size so rapidly that there is danger of its becoming too small at the fullered place before the operator is aware of it. When using the top fuller alone, in the same manner as the flatter ([Fig. 33]), similar precautions should be observed. If the metal is to be decreased between two shoulders, the top fuller may be used to rough it out; but the fuller marks should be distributed between the shoulders, until one of the set hammers or the flatter can be used.

If the metal is being drawn and is held crosswise on the anvil, as shown at a, [Fig. 34], it will increase in length more rapidly than it will in width, and if held lengthwise as at b, it will increase more in width than in length. This is due to the fact that the anvil is slightly convex on its face, so that it has the effect of a large fuller.

Fig. 34.—Drawing with the Hand Hammer.

The most difficult drawing for the beginner is to form metal into a square or hexagonal shape. To draw it into a square form, the metal must always be turned either one quarter or one half of a revolution to prevent its becoming diamond-shaped, and the blows must be delivered equally on the four sides to prevent its becoming oblong. If it does become diamond-shaped, it can be made square by delivering blows at a slight angle on the corners and sides of its long diagonal as shown at A, B, and C, [Fig. 35]. If it is but slightly diamond-shaped, the method shown at B will prove satisfactory, but if badly out of square, the method at A will be the best.

Fig. 35.—Squaring up a Diamond-shaped Piece.

In drawing the hexagonal form, the metal should be turned by sixths of a revolution. If it becomes distorted, it may be forged with such blows as are shown at B and C; if held as at A, it would be marred by the edge e.

54. Bending is the operation of deflecting metal from a straight line or changing its form by increasing the deflection already present. Iron of any cross-sectional shape can be bent, but some shapes are much more difficult than others.

The easiest to bend is the round, the only difficulty being to prevent the hammer blows from showing. If the metal is to be round in section when finished, the work will not have a good appearance if the cross section is oval at some places and round at others, and unless the hammer blows are cautiously delivered this will be the result.

Bending metal of a square section at right angles with the sides is not very difficult, but bending such a section in line with the diagonal is quite difficult, because the edges are liable to be marred where they rest on the anvil and where the blows are delivered. The best method of making bends of this kind is to heat the metal only where the bend is to be, and then to bend it by pressure or pulling, while the work is held securely in the vise, hardy hole, or swage block. If the heating cannot be confined to the desired space, all excessively heated parts should be cooled.

Oval sections are easily bent through their short diameters, but in bending through the long diameters, the same method should be pursued as described above for bending the square section in the plane of its diagonal. Further explanations for bending are given on pages [118]-121.

55. Upsetting is the operation of enlarging metal at some desired point or place. It is done by hammering, ramming, or jarring. When a piece of metal is too long it can be shortened by upsetting, or when it is too thin at a certain place it can be thickened by the same method. This is done by having the metal hot only at the point or place where the upsetting is required. It is frequently necessary to cool the metal where the heat is not needed in order to confine the upsetting to the desired place.

Upsetting is not a very difficult operation as long as the metal is kept perfectly straight; otherwise the task will prove tedious and the metal may break from the constant bending back and forth. Bending will always take place, but breaking generally can be prevented by having the metal hot when it is straightened. The greatest difficulty in this respect will be experienced when operating on common wrought iron.

Upsetting by hammering is done by holding the metal perpendicularly on the anvil or something solid enough to withstand the blows which will be delivered upon it. Figure [36] shows this method.

Fig. 36.—Upsetting by Hammering.

If the end of a bar is being upset, and the upsetting is supposed to extend up through the bar for some distance, the heated end should be placed on the anvil as shown in the figure, because the anvil will slightly chill the end of the bar, and the upsetting will continue much farther than if the blows were delivered on the hot end. Striking the hot end with the hammer increases the diameter of the end excessively, because the contact of the hammer does not have a tendency to cool the metal.

Fig. 37.—“Backing up” Metal.

Another method of upsetting with the hammer, which is called “backing up” the metal, is shown in [Fig. 37]. This method does not upset the metal so rapidly, because the force of the hammer blows jars the hand and arm which hold the bar.

Upsetting by ramming or jarring is thrusting the metal forcibly against some heavy object like the surface plate, the swage block, or the anvil. Figure [38] shows upsetting by this process. This method is very effective and is used mostly when the metal is long enough to be held with the hands, as shown.

Fig. 38.—Upsetting by Ramming.

56. Forming is a term generally applied to the making of a forging with special tools, dies, or forms. This process may include bending, punching, and other operations.

Swages are used for forming. A block of steel with a depression of a special design is known as a forming die; a number of other tools and appliances may be used for forming, but it is needless to mention them here.

57. Straightening is one of the most frequent operations. When metal is being forged, the various blows have a tendency to make it crooked, and if the work is supposed to be straight when finished, it should be so.

Fig. 39.—A, Straightening with the Hammer;
B, Straightening with the Swage.

There is as much skill required to straighten properly a piece of metal as there is to bend it. The most common method (A, [Fig. 39]) is to hold the metal lengthwise on the anvil with the bowed side or edge upwards, then to deliver the blows at the highest point of the bow. The blows will be most effective at the point where they are delivered, so they should be distributed in order to get the object perfectly straight and to avoid making unsightly hammer marks.

If the metal to be straightened is round, or if it is flat with round edges, it is best to use a top swage of the proper size and deliver the blows on the swage as shown at B, [Fig. 39]. Then the surface of the round or the edges of the flat stock will not show any marks. The flatter or round-edged set hammer may be used in the same manner on flat or square material.

Fig. 40.—Straightening Wide Metal.

When wide pieces of flat metal are to be straightened edgewise, and such blows as are shown at A, [Fig. 39], are not effective, then the blows should be delivered along the concave edge as shown in [Fig. 40], and distributed as indicated by the dotted circular lines. Blows delivered in this manner will stretch or lengthen the metal on the concave edge and straighten it.

58. Twisting is the operation of rotating metal to give it a spiral appearance. It may be done either hot or cold, as the dimensions of the material may require. It is done by holding the material in the vise, the hardy hole, or the swage block, and turning one end of it with a pair of tongs or a monkey wrench as many times as may be required. The twisting will be confined between the places where it is held with the vise, and where it is seized by the tongs or wrench.

If the material to be twisted is heavy enough to require heating, a uniform heat is necessary or the twist will be irregular, and, as an artistic appearance is usually desired, this operation should be carried out with that result in view.

Fig. 41.—A, Metal Twisted while Hot; B, Metal Twisted while Cold.

A, [Fig. 41], illustrates a piece of ¹⁄₂-inch square stock that has been twisted while hot. B shows a piece of ¹⁄₂ × ¹⁄₈-inch material that has been twisted cold.

Another difficulty met with in twisting a piece of metal is that of its becoming crooked. It can be straightened by laying the twisted portion on a wooden block and striking it with a wooden mallet. This will prevent the corners from becoming marred. A good method of avoiding this trouble is to twist the metal inside of a piece of pipe whose inside diameter is equal to the diameter of the metal.

59. Welding, the most difficult operation in the art of forging, is the process of joining two or more pieces of metal into one solid mass.

All the previous operations allow some time for thought; in welding, the worker must determine instantly where each blow is to be delivered, as the welding heat of the metal vanishes rapidly; therefore, he is compelled to think and act very quickly.

A scientific analysis of a perfect weld shows that it consists of several processes, and that each one must be perfectly executed. If any of these operations are improperly done, the result will be a partial failure; if they are essential ones, the weld may readily be considered as totally unfit.

60. The Material for Welding.—This must be considered, because there are different qualities in each metal to be operated upon, and some metals can be worked more easily than others.

A cross section of a bar of iron viewed through the microscope is seen to be made up of a great number of layers or fibers, called laminæ, resembling the grain or fiber in wood. These were cemented together in the process of rolling or welding in the mill where the iron was manufactured, and are continuous through its length. This makes the bar of uniform quality throughout.

In welding, these fibers are joined diagonally at the ends, consequently the strength of the weld depends entirely on how closely or perfectly this cohesion is made. Careful hammering at the proper heat brings the fibers in as close contact as possible, squeezes out the slag and scale, and therefore greatly assists in strengthening the weld.

Iron is an easy metal to weld. To prove this, place two pieces of iron in a clean, non-oxidizing fire, allowing them to attain a white or welding heat; then place them in contact and notice how readily they stick together, proving that iron is easily welded at the proper temperature. But in order to make the contact thorough, the pieces must be hammered. This shows that hammering is a secondary operation, and that iron cannot be joined by either heating or hammering alone.

By a similar experiment with soft steel, you will notice that the pieces do not adhere like iron. If borax is applied while they are heating, then slight indications of adhesion will be noticeable. This shows that borax, sand, or something of a like nature must be used in welding steel. In this case hammering is not a secondary operation, but an essential one.

A higher carbon or tool steel may be experimented upon, with nearly the same result. The noticeable difference between the lower and higher qualities of steel proves that the greater the quantity of carbon, the harder will be the welding, and if the experiments were extended to still higher carbon steels, it would be discovered that they could not be joined except by the use of a specially prepared flux. There are indeed some high carbon steels that cannot be welded.

If a forging is to be made of a special quality of material, it is frequently advisable to avoid welds, because two pieces that are welded can hardly be considered so strong as a piece of the same material that has not been welded.

The weldings which are alluded to here are such as are used by practical blacksmiths in their general work without any special appliances or apparatus whatever. The majority of the exercises on welding in this book require the use of iron; for this reason this preliminary consideration of metals need not have any further special attention.

61. Heating.—When the word “fuel” is used here, either coal or coke may be meant. Coal is the original in either case, for coke is formed from it by the removal of gaseous substances. It is better that the coal first be converted into coke, and that only the coke should come in direct contact with the heating metals.

Fig. 42.—Sectional View of a Blacksmithing Fire.

Figure [42] shows a sectional view of a blacksmithing fire: d is the bed of hot coke; c is the dampened and unburned coal which surrounds the fire, continually forming more coke as it is needed and also holding the fire in a compact form; a shows the proper way of placing the metal in the fire, b, the improper way because the metal is too near the entrance of the blast. As heating is such an important operation, a thorough understanding of what causes imperfect heats, as well as how to prevent them, is necessary.

The best fire for perfect heating is a reducing one, that is, one in which the combustion of the fuel is rapid enough to use entirely the oxygen in the air which is supplied. An oxidizing fire is one that does not use all the oxygen in the blast for the combustion of the fuel. The surplus oxygen will produce, on the surface of the metal, oxide of iron, or a black scale, which is extremely injurious. This scale will prevent welding, so all possible precautions should be taken to avoid its forming.

A reducing fire can be maintained, and an oxidizing one avoided, by having plenty of fuel surrounding the metal, equally, and allowing the entrance of only sufficient air or blast to provide the necessary heating.

If a piece of metal is left in a fixed position while heating, the lower side will become the hottest. For that reason, all metals to be welded are placed with scarfs downward. If the required heat is to be a penetrating and thorough one, the metal is turned frequently to bring all surfaces in contact with the most intense point of heat.

Even though every possible precaution is taken in all other steps of the welding, the pieces cannot be joined perfectly if the heating is carelessly done.

62. Scarfing.—This is the operation of preparing or shaping metal for welding. There are five general kinds of welds, the distinct form of each depending either on the quality of the material or on the shape of the desired forging. They are called the lap weld, the cleft weld, the butt weld, the jump weld, and the V weld.

63. The lap weld ([Fig. 43]) is so called because the pieces lap over each other when placed in contact. It is most commonly used in general practice, and all welds formed in a similar manner belong to this class, regardless of the sectional form of the material or the shape of the completed weld.

Fig. 43.—Lap Weld Scarfs.

The pieces should always be upset where the scarfs are to be formed, to provide excess metal for welding. They should be formed with their end surfaces convex, and at an angle of about 45 degrees, which would not make the joining surfaces too long.

When the fire and all tools are ready, place both scarfs face down in the fire; when they are removed to the anvil, the piece held in the right hand should be turned face up and rest on the anvil, in order that the other may be placed in position on top of it.

The left-hand scarf should be placed carefully, with its point meeting the heel of the other. If placed too high and overlapping, it will increase the surface to be welded and perhaps decrease the dimensions of the material where the points are welded down upon the exterior. If placed too low, in all probability the surplus metal provided by upsetting will not be sufficient to form the weld to a uniform dimension. A little practice with the scarfs before heating is advisable to prevent this difficulty.

The hand hammer should be placed conveniently on the anvil, with the handle projecting sufficiently over the heel so that it can be grasped quickly with the right hand as soon as the two pieces are in position. If this precaution is not taken, the welding heat may disappear before any blows can be struck.

The first blows after the pieces are placed should be directed toward the center of the scarfs; when the center has been thoroughly united, the blows should be directed toward the points to complete the operation, if this can possibly be done in one heating.

It is impossible to give an invariable routine of blows; those given are sufficient for the beginning, the rest must be left to the observation and skill of the operator. Practice and judgment will determine where the blows should be delivered, and when they should cease.

As the welding heat vanishes very rapidly, it requires careful judgment to determine when the pieces cease to unite. All blows delivered after this will reduce the dimensions of the metal; if reheating is necessary, there should be no metal sacrificed by unnecessary hammering. Welds are generally weaker than the metal from which they are made; consequently if the stock is made smaller at the weld, its strength is greatly decreased.

The old adage “Haste makes waste” does not always apply. If you hasten the operation of welding while the pieces are sufficiently hot, you will not waste the metal. If through want of haste you are compelled to reheat, you will waste metal, for every time a piece is heated it loses a fractional part of its area, regardless of any hammering.

Welds made with scarfs of this kind are considered to be nearly as strong as the metal itself, because they allow of a more thorough lamination by hammering than other welds, consequently they are frequently used on various qualities of metal when strength is considered a chief requirement.

Fig. 44.—A, Cleft Weld Scarfs; B, Butt Weld Scarfs.

64. The cleft weld (A, [Fig. 44]) is so called because one piece of metal is split to receive the other. It is used for welding iron to iron or steel to iron (the inserted portion being the steel). Whatever the metal, the inserted portion is usually roughened with a hot cutter on the pointed surfaces and the cleft hammered down and securely fitted before the whole is heated. The pieces should not be placed in the fire separately, but together, as they have been fitted.

When a welding heat appears, if possible, light blows should be delivered on the end of the inserted portion while the two are in the fire; these blows will partly join the pieces and make them secure before removal. If this cannot be done, the first blows after removal from the fire should be on the end. When a final and thorough welding heat has been attained, they should be removed to the anvil and securely joined. If heavy pieces are being operated upon, they may be welded with the steam hammer.

65. The butt weld (B, [Fig. 44]) is so called because the pieces are butted together and almost thoroughly joined by ramming or backing-up blows before any blows are delivered on the exterior surface. The scarfs are easily formed. The outer edges of the pieces are backed up to form a rounded or convex end to insure their being joined at the center first. As the blows are delivered on the end, the metal will upset and the pieces will be joined from the center to the outer edges. After they have been quite thoroughly joined with these blows, they should be hammered on their exterior to weld them securely.

When scarfed in this manner, the pieces are frequently placed in the fire for heating with the ends in contact, then partly joined while in the fire and removed to the anvil or the steam hammer for final welding.