To make a cold chisel.
1. Heat the steel to a cherry red, and shape the hammer end by holding it on the anvil, as shown in Figure 120. It should be noted that the left hand holds the metal well up, so that the taper made on the anvil side is at the same angle as that made by the hammer on the top side. Hammer it square by giving it a quarter turn as the hammering is done, then make it octagonal by hammering down the corners, and then round by turning and hammering. Shaping the end in this way tends to direct the force of the hammer blows down the center of the chisel when in use.
2. Hold the end against the face of the grinder, and grind the end down to solid metal, turning it as the grinding is being done.
3. Heat the other end of the chisel to a cherry red, and hammer it on one side and one edge to the shape suggested in Figure 121. Hammering the edges is to prevent the end from spreading out fan shape.
4. Cut off about % in. of the thin edge by use of the hardie.
5. Hold the cut end squarely against the grinder, and grind it back to solid stock.
6. Grind the chisel to an angle of about 70 deg. A template made of tin or galvanized iron, as shown at A, Figure 121, is handy in testing the angle. The template is 1 by 1 % in., and a notch is cut in one edge, in. wide and 5/16 in. deep, thus making an angle of about 70 deg.
7. Temper the chisel as follows:
a) Heat about 3 in. of the cutting end to a cherry red.
b) Dip about 1 in. of the end in water, moving it slightly up and down to prevent water lines or checks, and hold it in the water until the tip is cold.
c) Push an old file over one of the flat sides so that the color of the metal can be clearly seen.
d) Watch the color on the metal closely, noting that the cutting end is straw color, next to that a purple, and then a blue. The metal at the straw color is so hard that it would chip or break with use. The purple is also too hard for general use. When the purple is disappearing at the cutting edge and the blue has drawn down, the chisel is plunged in water, thus setting the metal at that temper.
8. Try the chisel on some iron. If it tends to dull up and bend at the cutting edge, it is an indication that it has become too soft by allowing the heat to draw down too much before it was plunged. In this case, reheat the chisel, and as the temper color draws down, plunge it in the water a little sooner. If, when trying the chisel, the edge chips off or cracks, it is an indication that o
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