Machining of Tapered Holes by Contouring with Slender Ball End Mills

概要

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This paper describes a method to machine tapered holes with slender ball end mills onto hardened steel for plastics molding dies. Tapered holes are usually finished with taper shaped ball end mills after the roughing with drills before hardening. But in order to eliminate the tool manufacturing period and machine time, direct cutting of hardened steel by helical feed milling with straight slender end mills was proposed. In this research, effects of feed direction on cutting tool life and machining accuracy was investigated. Experimental results revealed that tool life is longer in clock wise (CW) feed direction than in counter clock wise (CCW) direction although surface roughness is better in CCW. It was also found that the change of diameter of machined holes in CW direction is smaller than that in CCW direction because increase in cutting forces due to tool wear is smaller in CW direction than in CCW direction.