Next to the hammer in importance is the anvil. This may be any block of metal upon which the piece to be shaped is laid. The anvil must be of such a weight that it can absorb the blows that are struck upon it without experiencing any perceptible motion in itself.
It can be shown that if a body impinges upon another of equal weight, the two will thereafter tend to move at a velocity equal to one-half of that originally possessed by the impinging body. Suppose a sledge hammer weighing fifteen pounds to be moving at the rate of 10 ft. per second. If it were to strike Upon an anvil of the same weight the two (the hammer and anvil) would lend to move down at the rate of 5 ft. per second. But if. instead of this, it were to strike upou an anvil weighing 400 lbs. the tendency of the two (.the hammer and anvil) would be to move on at a speed of but .36 foot = 4.3 in. per second. This velocity is easily checked and absorbed by the elasticity of the blocking on which the anvil rests.
The ordinary anvil, Fig. 11, has remained unchanged inform for many hundreds of years. As now made, the body a is of wrought iron to which a face of hardened steel is welded. From one end there projects the horn b, and the overhang of the body at the other end e is called the tail. At the bottom there are four projections d, called the feet, which serve to increase the base upon which the anvil rents as well as to afford the means for clamping it down into position. In the tail there is a square and a circular hole. The former serves as a mortise in which cutters and similar tools may be held.
The anvil should he placed upon the end of a heavy block of wood sunken into the ground to a depth of at least two feet, so that it may rest upon a firm but elastic foundation. As the anvil is subjected to constant vibrations, by the nature of the work, it is necessary that it should be firmly fastened to the block. In doing this avoid spiking, as the spikes will soon work loose and the block be spoiled. A very convenient and reliable method of holding the anvil is shown in Fig. 12. Here, there are two iron rods about 3/8 in. in diameter passing over the feet of the anvil and running through a 1 inch round or square bar extending through the block. Nuts on these rods make it possible to draw them very tight and thus hold the anvil firmly.