heating furnace is likely to expand
tools, therefore provision must be made to leave extra stock to
take care of such expansion. Tools with shanks such as counter
bores, taps, reamers, drills, etc., should be heated no further
than they are wanted hard, and quench in oil. If a forge is not
at hand and heating must be done, use a muffle furnace and cover
small shanks with a paste from fire clay or ground asbestos. Hollow
mills, spring threading dies, and large cutting tools with small
shanks should have the holes thoroughly packed or covered with
asbestos cement as far as they are wanted soft.

CUTTING-OFF STEEL FROM BAR

To cut a piece from an annealed bar, cut off with a hack saw, milling
cutter or circular saw. Cut clear through the bar; do not nick or
break. To cut a piece from an unannealed bar, cut right off with
an abrasive saw; do not nick or break. If of large cross-section,
cut off hot with a chisel by first slowly and uniformly heating
the bar, at the point to be cut, to a good lemon heat, 1,800 to
1,850 deg.F. and cut right off while hot; do not nick or break. Allow
the tool length and bar to cool before reheating for forging.

LATHE AND PLANER TOOLS

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.F. 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 f