POLYCRYSTALLINE HARD SINTERED BODY CUTTING TOOL

PROBLEM TO BE SOLVED: To attain high machining accuracy and excellent machined surface roughness by specifying the radius of curvature of a curve produced in the intersection point part of a flank and a cutting face or a flank and a negative land face by cutting edge attaching operation. SOLUTION: A stepped support seat is provided in a corner part of a cemented carbide-made tool base material 2, a cBN polycrystalline sintered body 3 containing 20 vol.% or more of cBN particles having the particle diameter ranging from 0.01 μm to 5 μm is joined to the support seat by brazing, and then the sintered body 3 is subjected to cutting edge attaching operation to make a cutting tool. Cutting edge operation is performed by grinding using a diamond grinding wheel, and an intended cutting edge 6 is formed in an intersection part of a cutting face 4 and a flank 5. The cutting edge 6 is shaped like a section having a negative land 7 for strengthening the knife edge or like a section without a negative land, and the flank 5 and the cutting face 4 or the flank 5 and the negative land face 7 are connected to each other through a curve 8 with a radius of curvature of 0.1 μm to 5 μm.