facture of high-speed steel can only be obtained
by those companies who have become specialists. The art and skill
necessary in the successful working of such steel can be attained
only by a man of natural ability in his chosen trade, and trained
under the supervision of experts. To become an expert operator
in any department of its manufacture, it is necessary that the
operator work almost exclusively in the production of such steel.

As to the heat treatment, it is customary for the manufacturer
to recommend to the user a procedure that will give to his steel
a high degree of cutting efficiency. The recommendations of the
manufacturer should be conservative, embracing fairly wide limits,
as the tendency of the user is to adhere very closely to the
manufacturer's recommendations. Unless one of the manufacturer's
expert service men has made a detailed study of the customer's
problem, the manufacturer is not justified in laying down set rules,
for if the customer does a little experimenting he can probably
modify the practice so as to produce results that are particularly
well adapted to his line of work.

The purpose of heat-treating is to produce a tool that will cut so
as to give maximum productive efficiency. This cutting efficiency
depends upon the thermal stability of the complex hardenites existing
in the hardened and tempered steel. The writer finds it extremely
difficult to convey the meaning of the word "hardenite" to those that
do not have a clear conception of the term. The complex hardenites
in high-speed steel may be described as that form of solid solution
which gives to it its cutting efficiency. The complex hardenites are
produced by heating the steel to a very high temperature, near the
melting point, which throws into solution carbides and tungstides,
provided they have been properly broken up in the hammering process
and uniformly distributed throughout the steel. By quenching the
steel at correct temperature this solid solution is retained at
atmospheric temperature.

It is not the intention to make any definite recommendations as to
heat-treating of high-speed steel by the users. It is recognized
that such steel can be heat-treated to give satisfactory results
by different methods. It is, however, believed that the American
practice of hardening and tempering is becoming more uniform. This
is due largely to the exchange of opinions in meetings and elsewhere.
The trend of American practice for ha