Hard Turning of Steel

Hard turning of machine parts is a production process that holds considerable promise for the future since it is an effective means of increasing productivity. Instead of machining a product in the soft state, hardening the part by heat treatment, and then providing the required finish and dimensional accuracy by grinding, the expensive grinding operation is eliminated. This is possible because of the availability of improved hard tool materials (polycrystalline cubic boron nitride and ceramics), and more rigid machine tools. The nature of chip formation in hard turning is quite different than in more conventional machining. After reviewing the mechanics of this unique type of chip formation and the unusual tool orientation for carrying it out, experimental results are interpreted in terms of specific energy, the power required, and the surface finish to be expected. Authors: M. S. Shaw, A. Vyas, Arizona State University, Tempe, AZ.