View article

Hard machining is mainly a finishing or semi-finishing process used to machine workpieces having hardness 190-326 BHN where higher dimensional tolerances and accuracy has to be achieved. Case-hardened steel components having typical hardness-depth of just over 1 mm, giving it a wear resistant case and a tough core used in automobile axles are the typical example of hard machining that are converted from grinding process.[1]. Hard turning can provide a relatively high accuracy for many hard parts but sometimes important problems arise with surface integrity, especially with undesirable patterns of residual stresses and the changes of subsurface microstructure, so-called white layer, which reduces the fatigue life of turned surfaces [2]. In particular, the hard cutting process performed with ceramic or CBN tools can often cut manufacturing costs, decrease production time (lead time), improve overall product quality, offer greater flexibility and allow dry machining by eliminating coolants. By local plastic deformation some amount of material is removed from the cutting tool causing damage. Therefore, the flank wear occurring at the tool chip interface have to be periodically monitored. As the flank wear increases, the surface roughness on the machined surface of the specimen also increases in most of the cases.