Surface finish and lubrication at low cutting speeds

Abstract

Surface finish is one of the most important parameters to be controlled during machining as it affects many functional properties of components. It can be effected by workpiece and cutting tool material, geometry, cutting fluid, and cutting conditions. When machining at low cutting speeds a cutting fluid with good lubricant properties is often recommended to improve surface finish. This improvement is often thought to affect built up edge (BUE) formation, which is a major cause of poor surface finish. This work studies the effect of sulphur, an extreme pressure (EP) additive, in an oil lubricant on the surface finish of an AISI 1040 steel machined with a cemented carbide cutting tool. The application of a lubricant, with and without sulphur, does not prevent the formation of BUE but does affect the surface finish. This work suggests that the BUE is squeezed against the workpiece material close to the tool nose affecting surface finish. This region is where lubricant acts to improve surface quality and therefore very low volume of lubricant should be sufficient.