Abstract
Since cBN tool shows good cutting performance to the hardened steel, the authors has been considering to replace the grinding by the turning.
This paper presents new results of cutting tests performed on the orthogonal cutting with the cBN tool. Machining tests were conducted to find the most effective cutting conditions with long tool life for the finishing. Cutting speed was varied from 0.8 m/s to 3.3 m/s and rake angle ranged from -10° to -35°. The principal studies were carried out the relationship between edge shape and cutting mechanism, especially 'WHITE-LAYER' on the sawtoothed chip often observed at high cutting speed with large negative rake angle. The main results obtained are as follows: (1) The main cutting force and chip thickness has few influences to a variety of rake angle, and the cutting ratio comes near 1. Therefore, adoption of large negative rake angle for protection of the edge breakage has good advantages in the finishing. (2) It is concluded that the white-layer consists of an amorphous layer which is produced as a result of severe plastic defomation and rapid cooling.
