Fig. 110.
When cut off and hammered round on one end, the piece is caught with a fluted-lip pair of tongs that will hold it firmly and a ring is placed on the ends of the reins to bind them. The end is now heated in a well burned fire, letting the heat soak in slowly, and not forcing it with too much blast. If the fire is lively hardly any blast is used on the start. The piece is brought to a heat somewhat beyond what is commonly called cherry heat. It is then taken to the anvil and drawn out square with hard blows of the hammer, to a long taper, and nearly to a point. This taper should be about 1¾ inches long. See [Figure No. 111].
Fig. 111.
Hammering must cease before the red heat has left the steel. It is again heated and hammered on two sides; in drawing the chisel bends edgewise. Do not strike it on the edge; it will fracture the grain of the steel. To straighten the blade, it should be hammered on the flat side near the concave edge. See [Figure No. 112]. This stretches the metal and straightens the blade. Care must be taken in hammering not to make the chisel wider in one place than in another.
Fig. 112. Fig. 113.
When finishing the chisel, it is hammered lightly until the red is nearly but not quite gone. This hammering packs the grain and makes it fine. The end of the chisel is set on a hardie and cut half thru, so that when it is hardened and tempered it may be broken to note its grain and also require less grinding in sharpening. See [Figure No. 113]. The chisel is now heated very slowly to a dark red and set in a dry place on the forge to anneal. This annealing relieves the strain in the tool due to hammering.
When the chisel is cold it is reheated to harden and temper. Over-heating does not make the tool harder when cooled in water, but increases its brittleness, so care must be taken when heating. The heating must be very slow, and to a dark red, 2½ inches long. The chisel should be cooled as the heat is going up. A common practice of heating the steel more than a cherry red and holding it out of the forge until the heat goes down, before dipping, is wrong. When properly heated the chisel is held in a vertical position and dipped about 1½ inches into 16 gallons of salt and water, heated from 60° to 70° F. See [Figure 114]. The tool is kept in motion when dipped. When cooled it is removed, and the hardened part is rubbed bright with an emery stick or sand paper. This is done so that the temper colors may be seen. Tempering increases the tool’s elasticity and strength, and reduces the brittleness. The temper color will show just a faint yellow against the edge of the remaining heat that was left in the tool after hardening.