A Discussion on Tool Life Criteria and Total Failure Causes

Criteria based on crater wear and flank, wear (wear land) often mask the influence of other types of wear like chip notching on the rake face, primary groove (outer diameter groove) on the side cutting edge and secondary groove (oxidation) on the end cutting edge, all three of which are reported in this paper. Total failure is often wrongly correlated with the size of flank wear or crater wear. Our observations of optical and scanning electron micrographs show that total failure occurs either when the crater breaks into the secondary groove or when the chip notch breaks Into the primary groove, resulting in severe burnishing of the workpiece surface. Amongst the established criteria, crater index and surface roughness Ra are fairly reliable indicators of total failure. This paper highlights work done with HSS, cemented tungsten carbide, cemented titanium carbide and ceramic tools. © 1980 CIRP.