Lathe And Planer Tools
: HIGH-SPEED STEEL
: The Working Of Steel
FORGING.--Gently warm the steel to remove any chill, is particularly
desirable in the winter, then heat slowly and carefully to a scaling
heat, that is a lemon heat (1,800 to 2,000 deg.F.), and forge uniformly.
Reheat the tool for further forging directly the steel begins to
stiffen under the hammer. Under no circumstances forge the steel
when the temperature falls below a dark lemon to an orange color
about 1,700 deg.
. Reheat as often as is necessary to finish forging
the tool to shape. Allow the tool to cool after forging by burying
the tool in dry ashes or lime. Do not place on the damp ground
or in a draught of air.
The heating for forging should be done preferably in a pipe or
muffle 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 HIGH-SPEED STEEL.--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 to
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 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 TOOLS.--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.