Abstract
This paper describes studies on the failure of (Al,Ti)N coated sintered carbide ball end mill cutters used for the machining of hardened steel SKD11(HRC60) which has fairly large, very hard particles in the material. Theoretical analyses and a lot of cutting test are conducted. In the cutting tests all cutters had fatal failures at the boundary area, because real depth of cut at this area is extremely thin and chip generations are not so stable that these very hard particles cut the tool materials. Large pick feed distance and feed per a blade at high cutting speed produced very short tool lives. The longest tool life was obtained at the cutting of 15deg.work inclination angle.
