| abstract |
(57) [Summary] [PROBLEMS] To provide a tool using a polycrystalline hard sintered body, which has a small surface roughness of a machined surface and a high accuracy of a machined size. SOLUTION: The cutting edge is made of a polycrystalline hard sintered body 11 containing 20% by volume or more of cubic boron nitride. 5, the radius of curvature R of the cross-section is 5 μm or more and 30 μm or less, and the tool flank 12 and the tool rake face 13 or the negative land surface 14 are smoothly connected with the above-mentioned cross-section radius of curvature, The surface roughness of the cutting edge ridge portion 15 is configured to be not less than 0.1 μm and not more than 1.0 μm in ten-point average roughness (Rz). |