The role of lubricants in machining

Abstract Friction between the rake face of a tool and the freshly formed chip surface plays a vital role in influencing the ease of the metal cutting process. The existence of clean surfaces and high hydrostatic stresses favours the formation of strong adhesive friction junctions; the extent of these can be limited by the provision of a suitable lubricant. Experiments using a novel planing machine, which enables the orthogonal cutting operation to be carried out in carefully controlled atmospheres, are described; it is suggested that processes of molecular transport within a network of interfacial capillaries are dominant in controlling the effectiveness of cutting fluids provided they are capable of reaction with, or adsorption by, the metal surfaces.