But when the point gets heated up again, as it does by friction in
a lathe, it softens and loses its cutting edge. So the necessity of
keeping the tool cool limited the speed of the machine.
But about 1868 a Sheffield metallurgist, Robert F. Mushet, found that a
piece of steel he was working with did not require quenching to harden
it. He had it analyzed to discover the meaning of this peculiarity and
learned that it contained tungsten, a rare metal unrecognized in the
metallurgy of that day. Further investigation showed that steel to which
tungsten and manganese or chromium had been added was tougher and
retained its temper at high temperature better than ordinary carbon
steel. Tools made from it could be worked up to a white heat without
losing their cutting power. The new tools of this type invented by
"Efficiency" Taylor at the Bethlehem Steel Works in the nineties have
revolutionized shop practice the world over. A tool of the old sort
could not cut at a rate faster than thirty feet a minute without
overheating, but the new tungsten tools will plow through steel ten
times as fast and can cut away a ton of the material in an hour.
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