Geometrical Study on Machining Mechanism at Center of Ball-Nosed End Mill

Abstract

This paper presents a geometric analysis of an undeformed chip thickness at the top of tool in ball-nosed end milling. It has been firstly pointed out "backward cutting" near the center of tool that is irregular interference between the flank and the workpiece. So "backward cutting" occurs a non contact part on the cutting edge. Secondly a condition of "backward cutting" has been clarified. An area of "backward cutting" in a ball-nosed end mill is shaped circle that exists beside the center of tool axis. Thirdly a method of avoidance from "backward cutting" has been brought up. Then its influence for surface roughness is verified by a few experiments.