Until 1868, the steel tools used in lathes and drills, planers and so on, were limited to the moderate pace at which they remained cool enough to keep their temper. Beyond that quiet gait they became worthless, snapped apart, or melted as if wax. In 1868 Robert Forester Mushet, of the Titanic Steel and Iron Company, Coleford, England, discovered an alloy of steel, tungsten and manganese which took rough cuts at a depth and with a speed unknown before. This alloy, because hardened simply in air, was called “air-hardening” or “self-hardening.” Thirty years afterward at the Bethlehem Steel Works, Pennsylvania, a tool of this steel was heated to what was feared to be a ruinously high temperature; experiment proved that the tool could be used at a heat, and therefore at a speed, never attained before in the workshop. From that hour hundreds of investigators have proceeded to combine steel with tungsten in various percentages, adding manganese, molybdenum, chromium, silicon, and vanadium. Of these ingredients much the most important are tungsten and molybdenum. Particular pains must be taken thoroughly to anneal the alloy when worked into bars. As to the gain introduced by high-speed tool steels let Mr. J. M. Gledhill testify from the experience of the Sir W. G. Armstrong, Whitworth & Company’s works at Manchester:-- “Formerly where forgings were first made and then machined with ordinary self-hardening steel, a production, from bars eighteen and one half by six and five eighth inches, of eight bolts in ten hours was usual. With the new steel forty similar bolts from the rolled bar are now turned out in the same time, further abolishing the cost of first rough forging the bolt to form. The speed is 160 feet a minute, the depth of cut three-quarter inch, of feed 1/32 inch, the weight removed from each bolt sixty-two pounds, or 2,480 pounds per day, the tool being ground only once in that time. This is a fairly typical case. Just as striking is the behavior of this steel in twist drills, which supersede the punching process by passing through stacks of thin steel plates quite as swiftly and economically as a punch, while avoiding the liability to distress which accompanies the action of a punch.” With the quickening of pace due to these steels, the designer is asked to remodel machine tools so that they may stand up against new pressures and speeds. A lathe thus re-patterned is mentioned by Mr. Gledhill: it absorbs sixty-five horse power as against twelve formerly, and has a belt trebled in width so as to measure twelve inches. Mr. Oberlin Smith expects high-speed steel to have other effects on machine design than the conferring of new strength: he looks for a rivalry keener than ever between rotary and reciprocating tools. In his judgment the milling tool, which can be speeded indefinitely, will encroach more and more on the planer, limited as the planer is by its movement being to and fro.