e furnace, but if this is not convenient use a good clean
fire with plenty of fuel between the blast pipe and the tool. Never
allow the tool to soak after the desired forging heat has been
reached. Do not heat the tool further back than is necessary to
shape the tool, but give the tool sufficient heat. See that the
back of the tool is flatly dressed to provide proper support under
the nose of the tool.

HARDENING.--Slowly reheat the cutting edge of the tool to a cherry
red, 1,400 deg.F., then force the blast so as to raise the temperature
quickly to a full white heat, 2,200 deg.-2,250 deg.F., that is, until the
tool starts to sweat at the cutting face. Cool the point of the
tool in a dry air blast or preferably in oil; further cool in oil,
keeping the tool moving until the tool has become black hot.

To remove hardening strains reheat the tool to from 500 deg. to 1,100 deg.F.
Cool in oil or atmosphere. This second heat treatment adds to the
toughness of the tool and therefore to its life.

GRINDING.--Grind tools to remove all scale. Use a quick cutting,
dry, abrasive wheel. If using a wet wheel, be sure to use plenty
of water. Do not under any circumstances force the tool against
the wheel so as to draw the color, as this is likely to set up
checks on the surface of the tool to its detriment.

The Firth-Sterling Steel Company say:

INSTEAD OF PRINTING ANY RULES ON THE HARDENING AND TEMPERING OF
FIRTH-STERLING STEELS WE WISH TO SAY TO OUR CUSTOMERS: TRUST THE
STEEL TO THE SKILL AND THE JUDGEMENT OF YOUR TOOLSMITH AND TOOL
TEMPERER.

The steel workers of today know by personal experience and by
inheritance all the standard rules and theories on forging, hardening
and tempering of all fine tool steels. They know the importance of
slow, uniform heating, and the danger of overheating some steels,
and underheating others.

The tempering of tools and dies is a science taught by heat, muscle
and brains.

The tool temperer is the man to hold responsible for results. The
tempering of tools has been his life work. He may find suggestions
on the following pages interesting, but we are always ready to
trust the treatment of our steels to the experienced man at the
fire.

HEAT TREATMENT OF LATHE, PLANER AND SIMILAR TOOLS

FIRE.--For these tools a good fire is one made of hard foundry
coke, broken in small pieces, in an ordinary blacksmith forge with
a few bricks laid over the top to form a hollow fire. The bricks
shoul