Hard-Turning Grades Excel in Automotive Transmission Applications

Sandvik Coromant’s CB7125 and CB7135 grades are said to enable the performance of medium-to-heavy interrupted cuts and removal of the hardened layer (depth of cut up to 2 mm) in case- and induction-hardened steel components, typically for the automotive industry. For these applications, the two new grades offer longer and more consistent tool life, good levels of surface finish and consistent dimensional tolerances. The company says that those working with transmission and other hard-turned components can benefit from these grades, namely through added speed and a more secure edge line for lower cost per component. 

The two grades are optimized for turning steel materials with a hardness of 58 to 62 HRC. Designed for medium intermittent cutting, the CB7125 grade features a PVD coating that provides improved wear and fracture resistance for extended tool life. This grade, which contains medium CBN content, is ideal for turning shaft splines and shafts with chamfered oil holes or pockets. Further applications include gear facing, the hard-to-soft turning of crown wheels, and the removal of hardened layers.

The CB7135 grade is designed for the efficient longitudinal turning of gears and shafts with unchamfered keyways or pockets, as well as CV joint components such as the inner/outer race and cage. Featuring a high CBN content, the grade offers high fracture resistance and predictable machining results.

Available for the company’s T-Max P, CoroTurn 107 and CoroTurn TR tooling systems, the grades come in both positive and negative basic shapes, with various edge preparations.