Improving Hard Turning

While it is pointed out that using hard turning in place of grinding for case-hardened or induction-hardened steel components such as transmission shafts and gears can reduce both machining costs and time by as much as 70 percent or more, according to the people at Sandvik Coromant Co. (sandvik.coromant.com) such gains are achievable only if that hard turning (usually performed as a finishing or semi-finishing process) is performed with optimized insert grades. So the company has developed two new grades to address hard turning applications, CB7105 and CB7115, which use a PCBN grade material and coating (as well as specific edge prep).

CB7105 is said to provide better crater wear resistance and CB7115 better fracture resistance.

In a trial of the new insert materials, the production of case-hardened 16MnCrS5 (HRc 57-62) automotive components was increased by at least 15 percent after switching to CB7105 and CB7115. CB7115 surpassed 600 components (at 0.15 minutes time-in-cut) with predictable surface generation and lower Rz value. The cutting speed was 170 m/min (557 ft/min), while feed rate was 0.22 mm/rev (0.008 inch/rev) with a cutting depth of 0.15 mm (0.006 inch).