inished forged tool, and
let this grow cold by itself, the slower the better. It is well to
cool the tool slowly in hot ashes, to remove all forging strain.
You can now grind the tool dry on a sharp emery wheel. The more
you now finish the tool in grinding, the less there is to come
off after hardening.]

In hardening place the tool in a coke fire (hollow fire if possible)
with a slow blast and heat gradually up to a white welding heat
on the nose of the tool. Then dip the white hot part only into
thin oil or hold in a strong cold air blast. When hardening in
oil do not hold the tool in one place but keep it moving so that
it cools as quickly as possible. It is not necessary to draw the
temper after hardening these tools.

[Illustration: FIG. 89.--This tool is ground, ready for hardening.
Never harden from the forging heat.]

[Illustration: FIG. 90.--Heat the nose of the tool only up to dotted
line, very slowly and thoroughly to an absolutely white welding
heat, so that it shows a trifle fused around the edges, and be
very sure that this fusing has gone thoroughly through the nose,
otherwise the fusing effect will be taken off after the second
grinding. Note the difference of the nose between this and Fig. 86.]

[Illustration: FIG. 91.--Shows unnecessary roasting and drossing.
Such hardening requires a great amount of grinding and is not good.
After hardening grind carefully on a wet emery wheel, and be sure
that the wheel is sharp with a plentiful supply of water. Do not
force the grinding, otherwise the cold water striking the steel
heated up by friction, will crack the nose. Be sure that the grinding
wheel is sharp.]

In grinding all tools should be ground as lightly as possible on
a soft wet sandstone or on a wet emery wheel, and care should be
taken not to create any surface cracks, which are invariably the
result of grinding too forcibly. The foregoing illustrations, Figs.
84 to 91, with their captions, will be found helpful.

Special points of caution to be observed when hardening high-speed
steel.

DON'T use a green coal fire; use coke, or build a hollow fire.

DON'T have the bed of the fire free from coal.

DON'T hurry the heating for forging. The heating has to be done
very slowly and the forging heat has to be kept very high (a full
lemon color) heat and the tool has to be continually brought back
into the fire to keep the high heat up. When customers complain
about seams and cracks, in 9 cases o