Ball end mill

A ball end mill comprising:

• an end mill body rotated in an end mill rotation direction around an axis;
• a chip discharge groove located on a tip portion outer periphery of the end mill body, open on a tip flank of the end mill body, and extending to a rear end side in an axial direction;
• a concave groove-shaped first gash located in a tip portion of the chip discharge groove, and formed such that a bottom surface of the chip discharge groove is cut out to an inner peripheral side of the end mill body;
• and
• a bottom cutting edge located in a side ridge portion of the first gash on a tip outer peripheral side of a first wall surface facing the end mill rotation direction, and forming a hemispherical surface shape whose rotation locus around the axis has a center on the axis and is convex to a tip side,
• wherein the first gash includes
• the first wall surface,
• a bottom surface facing a tip outer peripheral side of the end mill body, and
• a groove bottom portion extending between the bottom surface and the first wall surface,
• at least the first wall surface of the first gash is provided with a concave groove-shaped second gash formed such that the first wall surface is further cut out at an interval from the bottom cutting edge, and
• a minimum curvature radius in a cross section orthogonal to an axis of the second gash is larger than a minimum curvature radius in a cross section of the groove bottom portion of the first gash.