| 摘要 |
Provided is a cutting insert (10) suitable for machining the inner wall surface of a pilot hole in an article to be cut. A groove (16) is formed in a corner section (12) of at least one polygon side surface of the cutting insert (10), which has an approximately polygonal plate-like shape. A tip cutting edge (13b) and an outer peripheral cutting edge (14b) are formed in intersecting ridgeline sections of two side surfaces which are adjacent to each other, with the corner section (12) in-between. In the intersecting section between the tip cutting edge (13b) and the outer peripheral cutting edge (14b), there is formed an auxiliary cutting edge (15b) which intersects with the outer peripheral cutting edge at an obtuse angle and also intersects with the groove (16). In that region of the groove (16) which is at least adjacent to such an area of the tip cutting edge (13b) as is in the vicinity of the corner section (12) and to the auxiliary peripheral cutting edge (15b), there is formed a scooping surface (17) that includes a downward inclined surface (16a), this downward inclined surface (16a) being such that the farther from the aforementioned cutting edges (13b, 15b), the closer to another polygon side surface on a gradual basis. The angle a formed by the direction M of the maximum inclination of the downward inclined surface (16a) and the direction along the tip cutting edge (13b) is larger than the angle ß formed by the aforementioned direction M and the direction along the auxiliary cutting edge (15b). |
