| 摘要 |
The present invention provides a cutting insert (10) suitable for machining an inner wall surface of a prepared hole in a workpiece. In the cutting insert (10) shaped like a substantially polygonal shape, a groove (16) is formed in a corner portion (12) of at least one polygonal surface, and at an intersecting portion between a leading cutting edge (13b) and an peripheral cutting edge (14b) formed at intersecting ridge portions of side surfaces adjacent to each other across the corner portion (12), a minor cutting edge (15b) is formed which intersects the peripheral cutting edge at an obtuse angle and also intersects the groove (16). Of the groove (16), at least in an area adjacent to the leading cutting edge (13b), which is close to the corner portion (12), and the area adjacent to the minor cutting edge, a rake face (17), which includes a downward inclined surface (16a) gradually approaching another polygonal surface as distances from the cutting edges (13b, 15b) increase, is formed. An angle ± between a direction M of maximum inclination of the downward inclined surface (16a) and a direction along the leading cutting edge (13b) is larger than an angle ² between the direction M and a direction along the minor cutting edge (15b). |
