Patent ID: 7878739

Claim:
A cubic boron nitride radius end mill having a cutting edge composed of sintered cubic boron nitride, comprising: a sintered cubic boron nitride compact bonded to an end of a main body; and the cutting edge provided on the sintered cubic boron nitride compact, wherein the wedge angle θt of the cutting edge is constant over the entire region of the cutting edge, a negative rake face is disposed on a face so as to extend over the entire region of the cutting edge, the rake angle θn of the negative rake face satisfies the relationship −30°≦θn≦−50°, and a joint cutting edge is disposed between an end cutting edge and a radius cutting edge in the cutting edge, the joint cutting edge having a concave angle γ0 which is smaller than the concave angle γ1 of the end cutting edge and which satisfies the relationship 0.5°≦γ0≦2°.