| 摘要 |
<P>PROBLEM TO BE SOLVED: To constantly keep a normal restraint surface, and to suppress the abnormal progress of the abrasion of a sub-cutting blade in comparison with a main cutting blade without any trouble in a clamp when changing the cutting blade. Ž<P>SOLUTION: A cutting insert is formed in a prismatic shape and a diamond shape in a plan view, and has a diamond-like upper surface 2a, a diamond-like lower surface, and four side surfaces 3. A main cutting blade 5 is formed of an edge in which the upper surface crosses the side surface and an edge in which the lower surface crosses the side surface. The side surface is composed of a first side surface 3a inclined outwardly from an edge of the upper surface to the center in the thickness direction, and a second side surface 3b inclined outwardly from an edge of the lower surface to the center in the thickness direction. A breaker groove 7 and a restraint surface 8 are formed at the first and second side surfaces alternately around a Z-axis, and deviated in the circumferential direction between the first and second side surfaces. A sub-cutting blade 6 is formed in a part having an acute angle formed between the breaker groove and the restraint surface out of the edges at which the side surfaces cross each other. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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