eldable.

STEEL FOR CHISELS AND PUNCHES

The highest grades of carbon or tempering steels are to be recommended
for tools which have to withstand shocks, such as for cold chisels
or punches. These steels are, however, particularly useful where
it is necessary to cut tempered or heat-treated steel which is
more than ordinarily hard, for cutting chilled iron, etc. They are
useful for boring, for rifle-barrel drilling, for fine finishing
cuts, for drawing dies for brass and copper, for blanking dies for
hard materials, for formed cutters on automatic screw machines
and for roll-turning tools.

Steel of this kind, being very dense in structure, should be given
more time in heating for forging and for hardening, than carbon
steels of a lower grade. For forging it should be heated slowly
and uniformly to a bright red and only light blows used as the
heat dies out. Do not hammer at all at a black heat. Reheat slowly
to a dark red for hardening and quench in warm water. Grind on a
wet grindstone.

Where tools have to withstand shocks and vibration, as in pneumatic
hammer work, in severe punching duty, hot or cold upsetting or
similar work, tool steels containing vanadium or chrome-vanadium
give excellent results. These are made particularly for work of
this kind.

CHISELS-SHAPES AND HEAT TREATMENT[1]

[Footnote 1: Abstract of paper by HENRY FOWLER, chief mechanical
engineer of the Midland Ry., England, before the Institution of
Mechanical Engineers.]

In the chief mechanical engineer's department of the Midland Ry.,
after considerable experimenting, it was decided to order chisel
steel to the following specifications: carbon, 0.75 to 0.85 per
cent, the other constituents being normal. This gives a complete
analysis as follows: carbon, 0.75 to 0.85; manganese, 0.30; silicon,
0.10; sulphur, 0.025; phosphorus, 0.025.

The analysis of a chisel which had given excellent service was as
follows: carbon, 0.75; manganese, 0.38; silicon, 0.16; sulphur,
0.028; phosphorus, 0.026. The heat treatment is unknown.

[Illustration: FIG. 83.--Forms of chisels standardized for the
locomotive shops of the Midland Ry., England.]

At the same time that chisel steel was standardized, the form of
the chisels themselves was revised, and a standard chart of these
as used in the locomotive shops was drawn up. Figure 83 shows the
most important forms, which are made to stock orders in the smithy
and forwarded to the heat-treatment room where