Machine drill
Place the forming tool in the anvil, and with a set hammer forge out the wings as shown in the sketch. The diameter of the drill depends upon the size of the hole to be drilled and is made accordingly. Use a sharp chisel for cutting the cutting edges of the drill. It is now ready for tempering. Drills are made in this way from the raw material. When once made they are kept in shape by what is known as the drill dressing tool shown here. These rock drills wear out on the sides, thus reducing the diameter. When re-dressing they are always upset to the required diameter. The re-dressing is done in the following way: Heat the end of the drill in the fire and place the dressing tool so that the cross impression fits the end of the drill. Drive on the end lengthwise of the bar, upsetting the drill to the required diameter, at the same time retaining the original shape of the cutting edge of the drill.
To temper rock drills: Take two small tubs of cold water, one clear and the other made soapy by cutting up a bar of cheap soap into bits. Heat the end of the drill to be tempered to a dull red and put it into the tub of clear water, the cutting edge only under water until it is cooled off. Take it out to polish. When the straw colour appears plunge it into the tub of soapy water. This does away with any red heat that might be in the bar when the temper colours appear. Soapy water is a poor conductor of heat and it allows the steel to cool off without suddenly chilling it.
DRILL FOR HAND DRILLING
These drills are used for drilling holes in rocks where it is impossible to place machines or where machines are not available, such as on farms, where great rocks and nigger heads are to be removed by drilling and blasting out.
They are made as you would make a cold chisel. The taper, however, is much shorter and the ends are usually either rounded or diamond shape. (See [sketch].) The cutting edges are ground, but in many cases they are forged and filed to shape. They are tempered in the same way as cold chisels are treated.
Round and flat hand drill