Patent ID: 7934890

Claim:
An end mill comprising: a plurality of chip discharge flutes in a helical shape located on an outer periphery of a tip portion of an end mill body which rotates on an axis; walls in the chip discharge flutes facing toward an end mill rotating direction are rake faces; and cutting edges formed along outer peripheral ridge portions on the rake face: wherein the chip discharge flutes comprise; at least one helix angle between the axis and the cutting edge in the chip discharge flutes of which are at least one or more are different from other helix angles between the axis and the other cutting edges in the other chip discharge flutes, and a cross-section perpendicular to the axis shows that a flute bottom face in a main flute portion, forms a concavely curved shape from the rake face to a point where the flute bottom face touches a web thickness circle of the end mill body, goes toward the end mill rotating direction; and also forms a linear shape from around the tangent point, and a flute bottom face in a sub-flute portion forms a linear shape, intersects with the flute bottom face in the main flute portion at an obtuse angle, goes further from the intersection toward the end mill rotating direction, and is connected to a flank face adjacent to the cutting edge toward the end mill rotating direction side.