_Stock:_ 1/4, 1/2, 5/8, 3/4-in. octagonal steel, 5 ins. long. Stone
chisels are made out of the above sizes of steel, in sets, for the
cutting of marble, sandstone, granite, etc.
_Directions:_ Put one end of the stock in fire. Heat about 1 in. Draw
this hot end to a taper 1/4 in. at the small end and 1-1/2 in. long.
Place the extreme end again in the fire, take it out and strike it on
the end by placing it upright on the anvil. Upset this end and form the
round top shown in the drawing. If this top is not completed in one
heating, heat it again and repeat the hammering on the end. All stone
chisels are made with this rounding end so that wood mallets can be
used for driving purposes. The ones shown here are the shapes used on
most stone chisels.
[Illustration: Stone chisels]
[Illustration: Stone chisels]
The size of the teeth depends upon the hardness or softness of the
material to be cut. The large teeth are used for hard stone cutting and
the small teeth for soft stone cutting. Place the other end of the tool
in the fire and flatten it down as shown in the sketch given here.
Notice the dotted lines show that the extreme cutting edge of this tool
is narrower than the body. This is an allowance made for the spreading
out of the tool while cutting the teeth. Space off the teeth with a
3-cornered file as shown in the same sketch, and cut the teeth with a
chisel made in the following way: Take a piece of 1/2-in. octagonal
steel. Draw it out in the shape of a cape chisel. (See sketch.) Heat
the end of the steel tool, then place it in the vise. With the end
projecting up place the chisel on the mark made by the file, strike
down sharply on the chisel, and drive it down to the required depth.
This is repeated until the teeth are all cut. Flatten the cutting edge
carefully on the anvil, and all teeth that may have been driven out
of a straight line by the cutting. Heat the tool to soften it. File
between the teeth the roughness made by the forging of the tool. A
small flat jewellers' file will be found best for this purpose. Harden
the tool as you did the cold chisel, and temper it at the purple
colour sign.