William L. Ilgen

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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