During early centuries the art of metal cutting made little progress except in-so-far as the application of greater driving power and the use of better machines were concerned. Lathes had been known since the sixth century B. C., at least, but, of course, little was or could be accomplished, comparatively speaking, before the invention of the steam engine by Watt, which was the first contrivance to give sufficient power for machining purposes. During the century which followed Huntsman’s time, steel makers and smiths became very expert in the manufacture and tempering of carbon steels. Lathe tools were made of these carbon steels, the only available material, but even with the better machine shop practice of the 19th century they were capable only of what we now consider to be inefficient results. The trouble was that since carbon tool steel gets its hardness from quenching from a red heat and then “drawing” the temper by reheating and slowly cooling from 400° or 500° F., tools made from it could not retain their hardness if their cutting points became much heated, as occurred if the lathe was run too fast. The usual cutting speed, therefore, was 20 or 30 linear feet per minute. Speeds in excess of this took the temper out of the tools and soon made them useless. About 1868 Robert F. Mushet, a metallurgist of Sheffield, England, made a momentous discovery. He found that a piece of tool steel which had cooled in the air was as hard as some of those which he had quenched. Being an investigator he set about discovering the reason for this experience which was without precedent. Analysis showed that beside the usual constituents of tool steel this particular bar contained tungsten, a comparatively new metal. He experimented with some hundreds of mixtures and evolved an alloy, which, in tools, would stand up under machine speeds double those which could be used with carbon steels. These new alloys became known as “air-hardening” or self-hardening tool steels because they required no quenching. The principal application of these new steels was in the cutting of harder metal than it had before been possible to cut, and little attention, apparently, was paid to the getting of greater outputs by increase of machine speeds. At this point Frederick W. Taylor of “efficiency” fame appears upon the scene. While manager of the Bethlehem Steel Works in the nineties of the last century, he was working upon the efficiency investigations for which he later became so famous. During his investigations, with Maunsel White he experimented with many air-hardening steels to determine the best grades to use for their shop work. Getting some inconsistent results they determined upon and made what was a most extended and systematic investigation, one so thorough and complete that Taylor and White have become part of the history of high-speed steels.