CUTTING INSERT WITH CHIP BREAKER, AND TURNING PROCESSING METHOD FOR HARDENED STEEL

摘要

PROBLEM TO BE SOLVED: To provide a cutting insert that is more inexpensive than a cBN cutting insert and that enables stable processing of hardened steel to be performed even in a condition of a cut depth greater than 0.5 mm.SOLUTION: A rhombic or triangular cutting insert has a hard coating provided on a surface of a base material (substrate) with a hardness of HRA92 or more. A cutting edge provided at an acute-angled corner part is made of a sharp edge that is not subjected to strengthening treatment; a cutting face has a face angle larger than or equal to 1° and smaller than 20°; and a chip breaker gently cut upward toward a central land part from the cutting face is provided.