Turning of hardened steel with interrupted and semi-interrupted cutting

This work studies the hardened steel turning with interrupted surfaces. Most of the works in this area is focused on continuous surfaces, rarely dealing with interrupted surfaces, so common in real workpieces. Among the tools used for turning hardened steels, CBN is outstanding. There is a tougher CBN grade, supposedly more suitable for turning interrupted surfaces and a thermal and chemical more stable CBN grade, supposedly suitable for continuous cutting. However a question remains: which class is most suitable for the turning of semi-interrupted surfaces? This work tries to answer this question. Aiming at this goal, several hardened steel turning experiments were carried out with three kinds of workpiece surfaces – continuous, interrupted and semi-interrupted – using the two grades of CBN tools cited above. Besides the verification of tool life, a detailed study about the occurrence which caused the end of tool life for all kinds of cutting was also carried out. The main conclusion points out that the low CBN content tool is more suitable for continuous and semi-interrupted surfaces. When cutting interrupted surfaces, the high CBN content tool presented a slightly longer life.