| 摘要 |
PROBLEM TO BE SOLVED: To provide a throw-away tip using polycrystal hard sintered body, capable of attaining low surface roughness of a finished surface and having high accuracy of finishing dimensions. SOLUTION: A cutting blade is formed of polycrystal hard sintered body containing 20 vol.% or more cubic boron nitride, the radius of curvature of the section of a cutting blade ridge line part ranges from 5μm to 30μm, a tool flank 12 and a tool cutting face or a negative land surface are smoothly connected with the above radius of curvature of section, and the surface roughness of a cutting blade ridge line part 15 ranges from 0.1μm to 1.0μm as the average roughness (Rz) of ten points. A straight blade is formed so that a pair of straight cutting blades L, L' directed from each terminal end of the nose radius r of the polycrystal hard sintered body toward the side of the throw- away tip respectively have a length ranging from 0.2 to 0.6 mm, and the angle made between a straight line bisecting the nose radius part and the straight line cutting blades, respectively, is 42°≤θ<SB>10</SB>,θ<SB>11</SB>≤45°. COPYRIGHT: (C)2003,JPO
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