Patent ID: 8277152

Claim:
An end mill having an end mill body rotatable on an axis, the end mill body comprising: a flute formed in a periphery of a top portion of the end mill body; and a gash formed in a top portion of the flute, wherein the gash has a shape which appears to be formed by cutting out a wall face of the flute which faces an end mill rotating direction, a wall face of the gash which faces the end mill rotating direction, is an end cutting edge rake face, an end cutting edge is formed along a top side ridge portion, a gash bottom face of the gash is formed between the end cutting edge rake face and the wall face of the gash which faces the rear side in the end mill rotating direction, respective connecting faces connect the gash bottom face to the end cutting edge rake face, and the gash bottom face to the gash wall face, the connecting faces have a concave curved shape or a substantially concave curved shape formed with straight lines in a cross-section perpendicular to an intersecting ridgeline between the end cutting edge rake face and the gash bottom face, one of the connecting faces which connects the gash bottom face and the end cutting edge rake face is a first connecting face, another connecting face which connects the gash bottom face and the gash wall face is a second connecting face, and either: a radius of curvature of the first connecting face is larger than a radius of curvature of the second connecting face in the cross-section, or a radius of a circle inscribed in the straight lines forming the first connecting face is larger than a radius of a circle inscribed in the straight lines forming the second connecting face in the cross-section.