Ceramic end mill and method for cutting difficult-to-cut material using the same

A ceramic end mill comprising:

• a cutting edge portion that includes a plurality of cutting edges and gashes, the plurality of cutting edges being arranged on a distal end portion side of a tool body in an axis direction spaced in a rotation direction, the gashes being formed between the cutting edges adjacent in the rotation direction, wherein:
• the respective cutting edges include center cut edges, end cutting edges, and peripheral cutting edges, the center cut edges being disposed from parts close to a rotation axis to an outer peripheral side in a radial direction, the center cut edges facing the rotation axis, the end cutting edges being continuous with the center cut edges, the peripheral cutting edges being continuous from the end cutting edges to a tool rear end side,
• respective center grooves are formed on rear sides of the center cut edges and the end cutting edges in the rotation direction continuous in the radial direction, the center grooves being continuous with positions where end cutting edge second surfaces face the rotation axis, alternatively, the center grooves being continuous with positions where the end cutting edge second surfaces approach the rotation axis, the end cutting edge second surfaces being laid between the center cut edges and the end cutting edges, the respective center grooves being formed between the end cutting edge second surfaces and the center cut edges positioned on a rear side of the end cutting edge second surfaces in the rotation direction, the center grooves passing on the rotation axis, the center grooves doubling as rake faces of the respective center cut edges, the center grooves being continuous with the inner peripheral side of the gashes in the radial direction,
• the end cutting edges have concave slope angles, the end cutting edge second surfaces inclining between the outer peripheral side in the radial direction and the rotation axis side from a distal end side in the rotation axis direction to a rear side of the tool body in the axis direction, and
• the center grooves and the end cutting edge second surfaces are arranged in alternation in the rotation direction of the rotation axis O at parts of the end cutting edge second surfaces close to the rotation axis.