A simple technique to characterize the role of work hardness in hard part machining

An experimental technique that employs a Jominy end quench test specimen for rapid characterization of the machining response of a steel with reference to its bulk hardness is presented. Employed widely by metallurgists to appraise the hardenability of a steel, the Jominy test entails the quenching of a standard cylindrical specimen from one end, on having heated it to the austenitizing temperature. The cooling rate at any transverse section of the specimen is therefore dependent on the distance of the section from the quenched end, which brings about a continuous variation of material hardness along its length. The use of such a specimen as the workpiece to investigate the machining response of the steel with respect to its hardness significantly reduces the time, effort and cost involved in reliably optimizing a hard part machining application. Cutting force and surface finish data are presented to demonstrate this simple, innovative concept.