END MILL AND ITS MANUFACTURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide an end mill which can more surely prevent forming of a streak on a cut surface in an end milling operation in which an end mill body 11 is axially advanced stepwise. SOLUTION: In the end mill in which a cutting edge portion 12 having external cutting edges 15 is formed at a tip end side of the end mill body 11 rotating about its axis and a shank portion whose diameter is smaller than that of the external cutting edges 15 is formed at a rear end side of the end mill body 11, a rear end portion 12a of the cutting edge portion 12 is formed such that the profile of an external cutting edges 15a rotating about an axis O is smoothly connected to the rotating profile of the external cutting edges 15 at the tip end side and approaches to the axis O in proportion to the distance toward the rear end side and in addition, the outer relieved flank 17a of the external cutting edges 15a is formed to be an eccentric flank having a convex curve in a cross section perpendicular to the axis O and having an outer relief angleβlarger than an outer relief angleθof the external cutting edges 15 at the tip end side.