In this research KP-4, one of the plastic mold steels, was coated with the AlTiN from one layer to four layers by the PVD method in the Ф cemented carbide ball end mill. Coated KP-4 was processed with various conditions. For example, slope of 15°, 30°and 45°the spindle rotation speed was changed from 10,000rpm to 16,000rpm, the tool feeding speed was changed from 1,300㎜/min to 1,700㎜/min, the depth of cut was also changed from 0.3㎜ to 0.9㎜, and etc. Cutting component force according to the coating layer number, surface roughness, and the wear of tool were studied.
