Part 11

_Directions:_ The end of this piece of stock is bent around a drift pin as shown in the drawing and welded along the dotted lines. This is done by scarfing the end of the bar into a short tapered point. Bend it down at right angles about 3 in. from the end. Bend it in the opposite direction about 2/3 of the way around. Put in the drift pin. This now forms a hook shape. Continue the driving over until the scarf lies flat on the straight side. Take out the drift pin and weld the scarf to the body of the hinge. Drive the drift pin into the hole, shaping it up. The back of the hinge is perfectly straight so that it will lie flat upon the wooden door. The other end is drawn out, tapered and the end rounded up, and 1/4 in. holes punched in as shown.

The butt is made in the same way as you made the ornamental butt and hinge.

Bent hinges, such as are used on tail boards for wagons, railroad cars, etc., are simply ends of the iron piece bent around at a given diameter, with the under side flat, and the stock rolled up on one side. These hinges may be used in pairs. In that case a long rod is pushed through, connecting the two hinges.

TONGS

Tongs are used by blacksmiths to hold pieces of hot metal while working upon them. _Stock:_ Two pieces iron, 7/8 × 7/8 × 18 ins. Two pieces iron, 3/8 × 3/8 × 12 ins.

_Directions:_ Mark off 2 ins. from one end of the 7/8 × 7/8 × 18 in. piece and heat it quite hot. This marked end is now placed on an anvil and flattened down to 1 × 2 × 7/16 in., leaving the shoulder as shown. (1) Heat the piece again. Place it upon the anvil, with the flattened piece extending beyond the anvil, and, with the shoulder on the outer edge of the anvil, flatten this down 1 in. wide, and 7/8 in. thick. (2) Then the shoulders should be at right angles to each other, as shown in the sketch. Re-heat the piece 1 in. from the last shoulder made. Reduce the shoulder (2), the iron to 9/16 × 7/16 in. (3) Notice that this shoulder is directly opposite the other. This completes the jaw of the tong. Draw out the end to about 3 ins. in length. It is now cut off the bar and another piece made just like it for the pair.

The reins or handles are welded to the small ends and tapered down as shown in the drawing, then rounded 4-1/2 ins. on the ends to 3/8 ins. in diameter. A hole is now punched through the eye of the jaw and a 3/8-in. rivet inserted. The little groove which you see in the jaw is put there with a fuller. This is done so that you can use it to hold small round iron as well as flat iron. The two parts are now riveted together. This is done either by making a head on a rivet and cutting it off, allowing about 3/8 in. for a head on the end that goes through the tongs, then heating the tongs and completing the riveting, or, as many smiths do, by putting a piece of straight 3/4-in. iron in, allowing 1/2 in. on each end plus the thickness of the parts of the tongs for riveting. This piece of iron is made very hot, put into the hole, and both heads are riveted on at the same time. It frequently happens that the rivet bends in the holes while hammering on the ends. This prevents the tongs from opening easily. If such is the case, put the rivet and jaws into the fire and heat red hot. Hold the handle, open and close the jaws while cooling. This not only centres the rivet but prevents sticking. The tongs should work smooth and free when cooled off in water.

XXIV

HARDENING AND TEMPERING: TOOL MAKING

EFFECTS OF CARBON ON STEEL

What is commonly known as carbon steel is a metal composed of iron containing varying amounts of carbon. Steels containing much carbon are called tool steels to distinguish them from the low carbon steels. Tool steel, when heated red hot and plunged into cold water, will harden, while low carbon steel treated in the same way will not do so. This is an excellent way of testing two bars of steel for carbon when one is not able to distinguish grades of steel accurately. It is carbon that gives the hardening quality. When steel is heated it becomes red at 1000° F. At 1300° F. it passes a point at which it absorbs considerable heat without any increase in the temperature, showing that some change in the structure of the metal must be taking place. If the steel is heated above this point and allowed to cool slowly, a brightening of the colour may be noticed as it passes this point, known as the point of recalescence. The brightening is due to a liberation of the heat previously absorbed.

_Method of heating steel in forge fires:_ All steel work, including tool dressing, hardening, and tempering, was formerly done in an ordinary forge fire. Now we have special furnaces for that purpose. However, in using a forge fire, care must be taken to insure good work. The fire must be very deep--that is, a large body of coke must be put between the tuyere, and the tool, so as to prevent the blast reducing the carbon on the surface of the steel. Sulphur will injure the quality of any steel tool. Hence, a fuel low in sulphur should be used. Charcoal is the best for this purpose, but the cost and the difficulty in maintaining the heat prevent its general use in blacksmith shops. If the coal does contain sulphur a great deal of it can be extracted or reduced by one making his own coke. This is done by burning the green coal to a coke and in this way driving off much of the sulphur. Gas furnaces or oil furnaces are used. This is much better than coal, for a uniform heat can be kept and an oxidation of the steel prevented. Whether natural or artificial gas is used, all that is necessary is to adjust the supply of gas in such a way that there will be a very slight excess of gas present beyond the proper amount for combustion. The presence of this gas excludes all air from the steel and therefore prevents its oxidizing the surface of the metal.

_Heating in lead:_ In order to prevent oxidation molten lead makes a most satisfactory bath. The lead is melted in a cast-iron pot and heated in the forge. The steel must be left in the bath until it has all been heated to the required temperature. As the steel will float in the molten lead it must be weighted down to keep it submerged.

_Hardening solutions:_ In many cases clear cold water is used in hardening steel. Some use soft or rain water. The temperature of the water for general work should not fall below the temperature of the shop; otherwise it would extract the heat too quickly from the steel and cause cracks or breaks in the work.

_Salt solution:_ Salt is often added to water which is to be used as a hardening solution. (1) It increases the rate at which the bath will extract the heat from the steel; (2) it prevents the formation of steam on the surface of the water. Put as much salt in rain water as it will dissolve. This is considered one of the best and easiest made solutions for hardening steel.

_Oil solution:_ Linseed oil, lard, cotton seed oil, whale oil, and melted tallow make good hardening solutions. They are used mostly for fine work. The oil prevents the sudden chilling of the steel and lessens the chances of cracking and breaking. Springs are mostly tempered in oil.

_Metallic hardening baths:_ For very delicate tools mercury is sometimes used. It has a greater heat conductivity than any solution mentioned. However, the fumes given off are poisonous and for this reason it is not extensively used.

TEMPERING: THE PART COLOUR PLAYS

When you buy steel for tools from a merchant he will assure you that the steel he sells you will harden at a cherry-red heat. This is true provided the metal has not been spoiled either by overheating it or working it at too low a heat during the making. This causes cracks or internal fractures.

If these directions for working steel are followed out a tool should harden at a cherry-red heat when plunged into water. When the steel is heated to the proper temperature, usually a cherry red, and plunged into a hardening solution, it will be very brittle, so that a file will not cut it. One test often used is to take a fine mill cut file and try to cut the hardened part of the tool. If it slips over the surface without cutting, the steel is considered hard; if the file cuts, the steel is not hard enough. Re-heat the steel hotter than before, cool it off in water, and test again. All cutting tools should possess a certain amount of hardness or toughness. When the steel has been plunged into cold water it is too hard for use. It is necessary to then reduce this hardness so that one can use the tool for the particular kind of work it is made to do. This process of reducing the hardness is commonly called drawing the temper, and the colour scheme plays a very important part in this operation. Perhaps the steps will be clearer if the process of drawing the temper on a cold chisel is explained: After the chisel is forged the proper shape, place the body of the tool in the fire, heat it red hot back of the point. Now heat the point to a uniform cherry-red heat, plunge 1-1/2 in. of this hot point into the water and hold it there until it is quite cold. This is determined by water clinging to the point when the chisel is taken out. Polish the part cooled off with a piece of emery stone, an old brickbat, or any rough polishing material. You will notice a group of temper colours starting from the point where the tool came into contact with the water. The heat in the body of the tool gives rise to these colours as it is conducted through the cold point of the steel. In this group of colours the first will be (1) pale yellow, (2) a full straw colour, (3) brown, (4) purple, (5) dark blue, (6) full blue, (7) light blue, (8) gray. This colour scheme corresponds to varying temperatures in the metal. The first colour (pale yellow) accompanies a temperature of 430°, while the last colour, gray, means a temperature of 700°. The colours show, too, a varying in the hardness or toughness of the steel. A cold chisel should be tempered a blue; so when the blue reaches the cutting end of the tool the end should be plunged immediately into water and cooled off. This is the principle of hardening and tempering all common tools.

However, these colours mean nothing so far as tempering is concerned unless the cutting edge of the steel has been thoroughly hardened. Then the colours have a real value. To prove that these colours are no test unless hardening precedes, take a piece of brass, or copper, or soft iron. Polish, then heat the piece in the fire to the temperature given here. You find the same set of colours, but you cannot use any of these metals for cutting tools.

The table of temper colours given in this book shows the colour required for tempering tools most commonly used.

_Tempering of springs:_ Under the head of springs we may include every variety, from the small spring used in locks and fire-arms to the largest springs in use. They are made of spring steel of the required thickness, forged into shape, then hardened and tempered.

This hardening and tempering of springs is done in some cases by polishing and heating over a fire and drawing them to a blue colour. Then they are plunged into oil to fix the temper. Sometimes springs are heated red hot and cooled in oil, then held over the fire until the oil burns with a bright flame on the spring. It is then allowed to cool in the air. If the spring is found too hard, more oil is put on it and the operation is repeated until the desired spring movement is obtained.

TOOL MAKING

It is possible for you to learn to make all of the tools you may need to use, including hammers. And not only will you be able to make blacksmiths' tools, but such as are used by carpenters, bricklayers, stone-masons, machinists, etc. You must not expect to be able to do this work at first, but in a little while you will be able to replace your first working tools with those of your own make. From time to time, as the tools break or wear out, you can repair them or replace them with new ones. This gives excellent practice in forging and handling steel, and prepares you for more and more advanced work, an experience necessary for doing any work well.

_Steel:_ There are many different grades of steel, depending upon the percentage of carbon contained in each. Steel low in carbon can be easily welded but cannot be tempered. Carbon steel is very difficult to weld and it can be done only by the use of borax or some other flux. High carbon steel or so-called tool steel, can be tempered. It is used for making cold chisels, files, drills, cutting tools, etc. _Crucible steel:_ All tools are made from crucible cast steel. The cast steel is made by placing in a graphite crucible a certain amount of wrought iron and soft steel, and carbon is added in the form of manganese. These are all melted in furnaces. When melted they are poured into ingots and drawn or shaped to sizes for the market under different kinds of power hammers. These various size bars are used for the making of all kinds of tools. The tools we are going to make are (1) centre-punch, (2) cold chisel, (3) cape chisel, and (4) lathe tools. There are five lathe tools; (1) round nose, (2) diamond point, (3) side tool, (4) cutting off or parting tool, (5) inside or boring tool.

_Centre-punch:_ You will find the centre-punch a most useful tool to have on hand. It is used for marking centres before drilling holes, starting points in work, etc. A small one is made out of a piece of 3/8-in. hexagonal tool steel, 3 ins. long. Put one end into the fire and taper it 3/8 in. long to 1/4 in. in diameter, as shown in the sketch. Make this end flat. Put the other end into the fire and draw it into a sharp tapered round point to about 1/16 in. on the end. This extreme point is ground to a very sharp point. The angles of the extreme should be about 45°. This is hardened and tempered a blue colour. Then it is ready for use.

_Cold chisel:_ Cold chisels are usually made out of 5/8-in. hexagonal tool steel, 6 in. long. The form and dimensions are given here.

Heat one end of the bar and place it upon the anvil. Draw it out for the short end. This is the part upon which the hammering is done when the tool is finished. The surplus stock is cut off with a hot chisel and the short end is flattened. When cutting tool steel of any kind the chisel should be very sharp and the steel red hot. Put the other end of the bar into the fire, beginning back about 2-1/2 ins. from the end. Flatten it down to a chisel shape, as shown in the drawing. Cut the surplus stock off, harden and temper as explained before for the cold chisel.

_Cape chisel:_ The drawing gives the form and the dimensions. The small end of this tool is forged out in the same way as you forged the small end of the cold chisel. Reverse the bar and heat the other end. Two inches back from the end fuller the metal down as shown in the drawing. Draw it out tapering. This end, too, is cut off, hardened and tempered as you did the cold chisel. Cape chisels are used mostly for cutting key ways in shafting. The point being wider than the rest of the blade gives clearance while cutting.

LATHE TOOLS

_Round nose:_ The drawing gives the form and the dimensions.

_Stock:_ A piece of 7/16 × 7/8 × 7 in. tool steel.

This size best fits the tool post of the lathe. You see by the sketch that one end is bevelled. This end is always made first. It is done by heating and chamfering the edges down with a hand hammer. Place the other end in the fire and draw it out to a sharp point in both directions. Throw the bevel on one side by placing the tool on the anvil and driving one side of the metal down to the other side. The point is now cut off on a bevel for clearance.

The drawing shows a cross section view of the tool. Notice that it is smaller on the bottom than on the cutting edge. This is done by reducing one side more than the other. The cutting edge of the tool should extend about 1/32 in. above the common level.

_Hardening and tempering:_ All lathe tools of this type are hardened and tempered in the same way as you did the cold chisel. The temper colour of this tool is a very light straw. When this colour reaches the extreme point plunge the tool into water. The slight change of temperature does not materially lessen the degree of hardness, but it does toughen the tool so that it will do more work.

_Diamond point:_ The form and dimensions are given.

_Stock:_ 7 × 7/16 × 7/8 ins.

Heat one end and bevel it off as you did when making the round nose tool. Place the other end in the fire, 5/8 in. from the end, and fuller down to one half the thickness of the bar. This fullering is done on the bottom fuller, which is placed on the anvil. Re-heat this end, place it again on the fuller in the depression made, and with the hand hammer draw this end out and at the same time square it up into a diamond point by turning the tool at an angle of 45° with the anvil. Turn again, in exactly the opposite direction. Repeat this until the point of the tool is drawn out as shown by the sketch. The clearance should not be more than that shown. It is now cut off by placing the face of the diamond on the outer edge of the anvil. Place the cold chisel above this edge, strike the chisel with the sledge hammer and cut it off. If this is carefully done it will cut the proper bevel for the cutting edge. The drawing shows the slope of the cutting edge to be parallel to the top of the tool. The tool is hardened and tempered the same as the round nose tool.

_Side tool (right hand):_ The form and dimensions are given here.

_Stock:_ 7 × 7/8 × 7/16 in.

To make a tool of this kind bevel off the end of the stock, place the other end in the fire, and heat about two inches to a red heat. Take it out and place about one inch of this on the round edge of the anvil. With the hand hammer reduce the thickness of this steel, driving on the edge nearest you (see sketch marked A). The hammering reduces the thickness of the edge, which will be the cutting edge when finished. The part opposite to where you are working will be reduced very little. A chisel is now used for cutting the cutting edge on the tool (see B). Place the tool on a piece of soft iron, place the chisel along the line and cut through to the soft iron below. This gives not only a clear cut but prevents the chisel from driving in if it should strike the hard anvil. The clearance is cut off along the other lines. (C) The cutting edge is now offset. To do this use a set hammer. Push the part made beyond the anvil 1/4 in. Place the set hammer in this shoulder, drive down until the offset is driven down about 1/8 in. (D).

The method of tempering this tool is a little different from the way you have tempered other tools, on account of the length of the cutting edge, which should be hardened its full length. Place the end just finished in the fire and heat to a red heat. Plunge the whole tool into water. Take it out and polish the cutting edge with emery stone. Now place in the fire a piece of any kind of iron; 1 in. square will do. Heat it red hot, then place it upon the anvil, and lay the part of your tool that has been hardened on the hot bar. It will draw enough heat from the hot bar to produce the temper colours. This is one way to give a piece of hardened steel the heat to temper it when the body of that piece does not contain heat enough to do so.

_Boring tool:_ Boring tools are made for the purpose of enlarging holes in cylinders, or any hole which should be enlarged after it has been drilled. The work to be done must determine the size and length of the boring tool. This is not true of any other one of the lathe tools.

_Stock:_ 7 × 7/16 × 7/8 in.

Bevel one end. Place the other end in the fire and heat about 3 ins. of it. Draw it out to a tapering octagonal shape, as shown in the sketch. The end is pushed over the anvil about 1/2 in. Drive it down at right angles. The clearance for the cutting edge is cut off with a hot chisel and made ready for hardening and tempering.

_Cutting-off or parting tool:_ This tool is made for dividing bars of metal into different lengths. The form and dimensions are here shown.

_Stock:_ 7 × 7/8 × 7/16 in. tool steel.

Bevel one end. Place the other end in the fire and heat about 1 in. Place the fuller on the anvil. Put the top fuller on this, then put the steel between the two fullers about 1/2 in. from the end. Using the sledge hammer, drive down so that the centre thickness will measure 1/8 in. Draw the lump left on the end to 1/8 in. thickness, the same width as the tool. The drawing shows that the clearance on this tool is one half the thickness of the cutting edge, or 1/16 in. This clearance must be put on as shown in the drawing, otherwise the tool will not clear while doing the cutting. Finish up as shown in the sketch. Harden and temper in the same way as you did the round nose tool. Cutting off tools are made with the shoulder all on one side. (See sketch and see article on tempering steel.)

XXV

HOW TO HARDEN, SOFTEN, AND STRETCH STEEL

ANNEALING OR SOFTENING OF STEEL

All steels that are worked under hammers and heated to any degree of temperature, when finished should be softened by heating, so that the unequal strains caused by the working of the metal may be neutralized. When the work is entirely finished it is placed in a furnace or forge fire and heated red hot. Then the fire is either withdrawn from the furnace, or the blast is shut off from the forge, and the metal is allowed to cool off as the fire goes down. This softens the metal and saves it from the danger of unequal strains.

Hard or high carbon steels are treated in a different way. The metal is heated red hot, then it is placed in a box filled with slack lime. The lime completely covers the piece. The cold air is prevented from striking it and cooling it off too quickly. When no lime is at hand wood ash can be used.

Sometimes the steel is heated red hot, then held until the red entirely disappears. Then it is plunged into cold water. This process is known as water annealing and is a process used for tool steel when quick work is required. It softens the metal so that it can be filed and worked quite easily.

CASE HARDENING

We have learned that carbon gives the hardening quality to steel. Since there is little carbon in soft steel and none in wrought iron, they will not harden as carbon steel does when heated red hot and plunged into water. But there are many small articles which are best made of this soft steel and iron and which must be hardened in some way to make them useful. In order to supply the lacking carbon the metal is put through a process known as case hardening. There are two methods of case hardening. The first method is to heat a piece of soft steel or iron red hot and cover the part to be hardened with cyanide of potassium. The metal will absorb the carbon out of the cyanide and when cooled in water will have taken on a hardened surface. If this is repeated two or three times the hard surface deepens.

Any drug store will sell you some cyanide of potassium. It comes in cakes. The cakes are broken up into small pieces. Be careful to keep the hands as much as possible from contact with the cyanide.

SET SCREW