End mill with throw-away tip

摘要

An end mill includes a body having a core receiving recess and a cutting insert releasably mounted thereon. An upper surface of the insert has a first cutting edge ridge serving as an outer peripheral cutting edge, a second cutting edge ridge providing an end cutting edge and a third cutting edge ridge providing an inner peripheral cutting edge. The upper surface has a corner where the second and third cutting edge ridge intersecting each other. The upper surface is composed of a central portion and a corner portion including the corner, whereby the third cutting edge ridge comprising a first edge portion defined by a ridge of the corner portion and a second edge portion defined by a ridge of the central portion. At least that portion of the corner portion disposed adjacent the central portion is inclined providing a thickness of the insert is progressively reduced toward the corner. The insert has a negative radial rake at the outer peripheral cutting edge and a positive axial rake. The second edge portion extends radially outwardly of the body and in a direction opposite to the direction of rotation of the body from that point where the first and second edge portions intersect. The distance between the corner and the axis is longer than between the axis and a point at which a line extending radially outwardly of the body from the axis and a line on which a corner ridge lies cross at right angles.