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.