The availability of polycrystalline cubic boron nitride tools has made the single-point turning of hardened steels a viable alternative to grinding for the production of precision parts such as injection molds and rollers for bearings. However, factors such as undesirable deformation and vibration of the machine tool, and rapid tool wear, still severely limit the quality of surfaces which can be produced by this process. The purpose of this project is to develop a better understanding of the mechanics and dynamics of finish hard turning. Work to date has focused on the morphology of chips formed during the cutting process. Orthogonal cutting experiments have been performed in which cutting speed, rake angle, and depth of cut were varied. Chips were found to be highly segmented at cutting speeds which exceeded approximately 0.5 m/s, and the onset of segmentation was accompanied by a rapid decrease in specific cutting forces. Subsequent examination of etched chip cross-sections using scanning electron microscopy indicated that the segmentation resulted from the localization of plastic strain into narrow shear bands. The average spacing between shear bands was found to increase monotonically with depth of cut, decrease with increased rake angle, and increase with cutting speed. Additional post-test analysis revealed that chip segmentation becomes more periodic with increasing cutting speed. The variation with rake angle and depth of cut can be explained using arguments based on the experimental geometry. However, an understanding of the mechanics and dynamics of the material removal process is required to explain the dependence of segmentation on cutting speed, and this must be understood in order to make accurate estimates of cutting forces. A quasi one-dimensional model of the elastic-plastic deformation of a workpiece of material by a rigid tool has been developed. Since the model is considerably simpler than those based on large finite element codes which are typically used to simulate cutting mechanics, it can be used to help elucidate the basic phenomena responsible for chip formation. The model gives results which are consistent with experiment, in the sense that numerical simulations also show a progression from continuous to segmented deformations in the chip removed from the workpiece, with the deformation patterns becoming more periodic with increasing cutting speed. In future work, the model will be improved in order to make its predictions more quantitative, and other materials of industrial interest, such as aluminum alloys, will be studied.