[Illustration]
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.
[Illustration: Round and flat hand drill]
[Illustration: Pipe drill]
_Round and flat hand drill:_ Take a piece of octagonal steel, the size
and length depending upon the size and depth of the hole to be drilled.
These should not be over 20 ins. in length, for the blow would have
little effect upon the cutting edge of the drill. Put one end into the
fire, take it out and finish it up as you would the short end of a
cold chisel. Reverse the piece of steel, and heat this end, for about
two inches, red hot. Place it on the side of the anvil face and flatten
it down tapering. Make it very short and just wide enough for the size
hole to be drilled. With a hot chisel cut the end into the proper
shape, either round or diamond shape. With the hand hammer work the
cutting edge on the end. This end should be from 1/8 in. to 3/16 in. in
thickness. Either file or grind the bevel which forms the cutting edge
sharp. Harden and temper it the same as you would a cold chisel. If it
is found, on trial, to be too soft, re-heat, harden, and temper at a
higher colour. One of the best hand drills for drilling holes in soft
material like bricks or sandstones is a piece of gas pipe any length.
File teeth in the end, like a saw tooth. Case harden the end. This
drill will go through a wall almost as quickly as a twist drill and
with much less labour.