For Students
In order to remove chips from a workpiece, a cutting tool must be harder than the workpiece and must maintain a cutting edge at the temperature produced by the friction of the cutting action. Steel with a carbon content ranging from 1 to 1.2 percent was the earliest material used in machine tools. Tools made of this carbon steel are comparatively inexpensive but tend to lose cutting ability at temperatures at about 400° F (205° C). In 1900 the introduction of high-speed steel permitted the operation of tools at twice or three times the speeds allowable with carbon steel, thus ...(100 of 6816 words)
