Radius end mill and cutting work method

A radius end mill, comprising

• a cutting edge portion disposed on a distal end portion of a tool body, the cutting edge portion including:
• a plurality of end cutting edges arrayed around a central axis;
• a plurality of arc-shaped radius end cutting edges continuous with the end cutting edges on an outer peripheral side in a radial direction;
• and
• a plurality of peripheral cutting edges continuous with the radius end cutting edges on an outer peripheral side in a radial direction, the peripheral cutting edges being disposed to extend to a rear end portion side of the tool body along cutting edge grooves, wherein:
• each of the plurality of end cutting edges is divided into an inner peripheral side end cutting edge and an outer peripheral side end cutting edge in a radial direction,
• each of the plurality of radius end cutting edges has a shape such that, for each of the plurality of radius end cutting edges, a lowest point of the radius end cutting edge during cutting with the tool body is positioned in a section from a boundary between the outer peripheral side end cutting edge and the radius end cutting edge to a boundary between the radius end cutting edge and the peripheral cutting edge,
• respective second surfaces of the plurality of all the inner peripheral side end cutting edges are coupled to one another at a part close to the central axis, such that the second surfaces of all the inner peripheral side end cutting edges are respective portions of a single continuous surface that includes a central region, which intersects and surrounds the central axis, the single continuous surface extending radially from the central region to an outer peripheral side of each of the inner peripheral side end cutting edges in a strip shape,
• a width of the strip-shaped region gradually enlarging from the central axis side to an outer peripheral side in a radial direction, and
• end portions of all the inner peripheral side end cutting edges close to the central axis intersect with the boundary lines between the second surfaces of the inner peripheral side end cutting edges positioned on front sides of the inner peripheral side end cutting edges in a rotation direction and gashes formed on rear sides in the rotation direction at positions on an outer peripheral side with respect to the central axis O in a radial direction.