Patent ID: 8740510

Claim:
A cutting insert, comprising: an upper surface; a lower surface; a side surface; a cutting edge comprising a main cutting edge, an auxiliary cutting edge arranged so as to make an obtuse angle to the main cutting edge in the upper surface view, and a corner cutting edge positioned between the main cutting edge and the auxiliary cutting edge, the cutting edge being located in at least a part of an intersection portion between the upper surface and the side surface; and a groove portion located on the side surface corresponding to the main cutting edge so as to reach the upper surface and comprising a first side wall surface positioned on the side near the corner cutting edge, wherein the first side wall surface is substantially parallel to the auxiliary cutting edge or comes close to the auxiliary cutting edge toward inside of the groove portion in the upper surface view, the main cutting edge comprises a plurality of separate main cutting edges divided by the groove portion, and the separate main cutting edge comprising both ends connected to the groove portions among a plurality of the separate main cutting edges comprises two curved cutting edge portions on the both ends in the upper surface view, the two curved cutting edge portions of the separate main cutting edge comprise a first curved cutting edge portion on the side near the corner cutting edge and a second curved cutting edge and have substantially arc shapes in the upper surface view, and curvature radius of the first curved cutting edge portion is larger than curvature radius of the second curved cutting edge portion.