Microscopic study on chips formed by sharp and bevelled turning carbide inserts

Abstract

The geometry of the cutting tools plays a significant role in tool performance and overall machinability characteristics, and further improvement is possible by appropriate modification of the geometry of the cutting edges. Modern cutting-tool materials possess high hardness and wear resistance, but are very brittle, which often results in premature and undesirable brittle failure of cutting tools. In continuous machining operations such as turning, this would increase rejection levels and the possibility of machine-tool damage, which poses a serious problem with sophisticated and expensive systems such as CNC machines, machining centers, FMS, etc. It has been established already that proper bevelling of the cutting edges enables reduction in cutting forces and improvement in the life of tools such as carbides and ceramics through: (i) edge strengthening; (ii) the controlled-contract cutting effect; and (iii) enhanced heat dissipation. To derive the maximum benefit from such edge bevelling, it is essential to explore its influence on the mechanism of chip formation and the role of the geometrical parameters of the land, individually and combinedly on the chip characteristics and the machinability indices: the present work has been in this direction. The results of such work are expected to be quite helpful to the manufacturers and users of cutting-tool inserts of carbides, ceramics and other brittle tool materials.