Single-step superfinish hard machining: Feasibility and feasible cutting conditions

A major inefficiency in the manufacturing of hard, high precision parts is the number of processes, or steps, currently needed. For instance, the current method of producing the surfaces of bearing races involves annealing, rough turning, hardening, several types of grinding, and, finally, abrasive based superfinishing. There is always an additional set-up for each additional process, and an occasional inspection between processes. Therefore, there has been an economic motivation to study methods of extending one process or one machine tool's capability so that other processes in the production sequence can be eliminated, thus, reducing set-up time and the complexity of manufacturing scheduling, and gaining significant benefits for flexibility and system efficiency. The concept and feasibility of using a single step for machining hardened steel to a surface comparable to that of lapped bearing races were presented briefly with limited data (Liu and Mittal: J. Mfg Syst. 14(2): 129-133, 1995). In this paper, extensive literature review and considerable data on surface waviness, profile, finish, microstructure and residual stress confirm the feasibility of the proposed new processing concept. The cutting conditions for producing a specific surface finish ranging from 2 to 8 mu in. are also presented.