The ultimate sharpness of single-crystal diamond cutting tools—Part II: A novel efficient lapping process

As the theoretical predictions presented in Part I, the ultimate sharpness of (1 1 0)–(1 0 0) oriented diamond cutting tool can reach up to 1∼6 nm, and the (1 0 0)–(1 0 0) oriented cutting tool up to 2∼5 nm [W.J. Zong, K. Cheng, D. Li, T. Sun, Y.C. Liang, The ultimate sharpness of single-crystal diamond cutting tools—Part I. Theoretical analysis and predictions, International Journal of Machine Tools and Manufacture 2005, submitted]. In order to validate the theoretical predictions, a novel efficient lapping process, namely thermo-mechanical lapping, is developed in the present work, which is regarded as an effective extension of the traditional mechanical lapping process. By this developed lapping method, a large number of lapping experiments are carried out on the (1 1 0)–(1 0 0) oriented cutting tools. AFM measurement results illustrate that lapping time has little effects, but both lapping compression force and lapping velocity have enormous influences on the finished cutting-edge radius. Furthermore, based on the optimized lapping compression force and lapping velocity, an elegant diamond cutting tool oriented along (1 1 0)–(1 0 0) is sharpened. Atomic force microscope (AFM) and scanning electron microscope (SEM) measurement results indicate the cutting-edge radius has been sharpened down to 2∼9 nm, which agrees well with the theoretical predicted value, i.e. 1∼6 nm.