End insert of cutting insert, indexable ball end mill, and indexable ball end mill

摘要

In this cutting insert (1), the rake surface, the seating surface (3) that faces the insert mounting seat facing away from the rake surface, and the flank surfaces extending around the rake surface and the seating surface (3) (4), and at the ridge line crossing the rake face and the flank face (4), the arc-shaped cutting edge (5a, 6a) extending in an arc shape and the arc-shaped cutting edge (5a, 6a) Two cutting edges (5, 6) having linear cutting edges (5b, 6b) in contact with each other are formed, and the seating surface (3) can abut on a projection projecting from the bottom surface of the insert mounting seat A groove portion (8) having various wall surfaces (8b) is formed, and the groove portion (8) is a narrow portion (9) in which the groove width narrows from one end side to the other end side in the extending direction of the groove portion (8). have.