Patent ID: 7402004

Claim:
A radius end mill in which end cutting edges and substantially arc-shaped corner cutting edges are formed on a tool body that is rotated around an axis wherein: chip discharge flutes that are helically twisted are formed on an outer circumference of a distal end portion of the tool body; main gash faces whose angle of inclination with respect to the axis is a smaller anger than a twist angle of the chip discharge flutes are formed on inner circumferential sides of distal end portions of wall surfaces of the chip discharge flutes that face in a direction of rotations of the tool, the end cutting edges are formed on a distal end of the main gash faces, and sub gash faces whose angle of inclination with respect to the axis has been made greater than that of the main gash faces are formed on an outer circumferential side of the main gash faces such that they extend away via step portions from the main gash faces, wherein the corner cutting edges that have a protruding arc-shaped contour are formed so as to be continuous with an outer circumferential side of the end cutting edges from a distal end as far as an outer circumference of the sub gash faces; and the step portions are formed as planar wall surfaces that are perpendicular to the main gash faces and sub gash faces.