will find a coarse grain with many bright spots
like crystals to the hardening depth. If uneven heating is the
cause, you will find a wider margin of hardening depth on one side
than on the other, or find the coarse grain from over-heating on
one side while on the other you will find a close grain, which
may be just right. If you find any other faults than a "pipe,"
or are not able to harden deep enough, then take the blame like
a man and send for information. The different steel salesmen are
good fellows and most of them know a thing or two about their own
business.

For much work a cooling bath at from 50 to 75 deg.F. is very good both
for small hobs, dies, cutter plates or plungers. Some work will
harden best in a barrel of brine, but in running cold water, splendid
results will be obtained. Cutter plates should always be dipped
corner first and if any have stripper holes, they should first
be plugged with asbestos or fire clay cement.

In general it may be said that the best hardening temperature for
carbon steel is the lowest temperature at which it will harden
properly.

CARBON IN TOOL STEEL

Carbon tool steel, or "tool steel" as it is commonly called, usually
contains from 80 to 125 points (or from 0.80 to 1.25 per cent)
of carbon, and none of the alloys which go to make up the high
speed steels. This was formerly known also as crucible or "cast"
steel, or crucible cast steel, from the way in which it was made.
This was before the days of steel castings. The advent of these
caused so much confusion that the term was soon dropped. When we
say "tool steel," we nearly always refer to carbon-tool steel,
high-speed steel being usually designated by that name.

For many purposes carbon-steel cutters are still found best, although
where a large amount of material is to be removed at a rapid rate,
it has given way to high-speed steels.

CARBON STEELS FOR DIFFERENT TOOLS

All users of tool steels should carefully study the different qualities
of the steels they handle. Different uses requires different kinds of
steel for best results, and for the purpose of designating different
steels some makers have adopted the two terms "temper," and "quality,"
to distinguish between them.

In this case temper refers to the amount of carbon which is combined
with the iron to make the metal into a steel. The quality means
the absence of phosphorous, sulphur and other impurities, these
depending on the ores and the methods o