This review considers the three major aspects of metal machining: the physical characteristics of chip formation, the properties and operating conditions of cutting tools, and the condition of the final product. There is a brief account of specialized metal-removal techniques and numerical and computer control of modern lathes and milling machines. T h e contributions of applied physics to metal cutting are emphasized throughout. T h e dependence of chip formation on the deformation and fracture behaviour of the workpiece and the friction conditions between chip and tool are described. At low cutting speeds, lubrication by cutting fluids or atmospheric constituents is important but the usual principles of tribology are invalidated by the intimate conditions of contact. At high speeds the response of the deforming material to the localized generation of high temperature and strain rate becomes important. Large shear strains are generated at all cutting speeds. Because of these extreme conditions the choice of tool materials is very restricted. Only recently have methods become available for detailed study of temperature and stress distributions in cutting tools, but wear and interfacial adhesion phenomena are dominant factors in practical performance. As workpiece materials are developed for improved strength and particularly for creep-resistance, the interrelated problems of tool wear and stock surface integrity become more severe.