Abstract: A cutting insert includes an insert body portion and a plurality of projecting portions provided integrally with the insert body portion. The projecting portion includes a cutting edge and includes projecting portion upper and lower surfaces, two projecting portion side surfaces, and a projecting portion side end surface extending therebetween. In the projecting portion, a round corner surface extends between the projecting portion upper surface and the projecting portion side end surface. The cutting edge is formed so as to include a corner formed along an edge of the round corner surface and such that the projecting portion side surface serves as a rake face. The projecting portion is designed such that a length between the two projecting portion side surfaces is smaller than a diameter of an inscribed circle defined on the insert body portion.

Abstract: A cutting insert has a first cutting edge provided with a chip breaker suitable for cutting an outermost region of a hole. The cutting insert has a substantially polygonal upper face, a substantially polygonal lower face, and a plurality of side faces extending between the upper face and the lower face. The plurality of side faces include a main side face constituting a flank of a linear cutting edge and a sub side face constituting a flank of a corner cutting edge; the main side face has a relief angle of 0°, the sub side face has a relief angle larger than 0°. A second cutting edge is further provided at an intersection portion between the main side face and the lower face.

Abstract: A cutting insert includes an insert body portion and a plurality of projecting portions provided integrally with the insert body portion. The projecting portion includes a cutting edge and includes projecting portion upper and lower surfaces, two projecting portion side surfaces, and a projecting portion side end surface extending therebetween. In the projecting portion, a round corner surface extends between the projecting portion upper surface and the projecting portion side end surface. The cutting edge is formed so as to include a corner formed along an edge of the round corner surface and such that the projecting portion side surface serves as a rake face. The projecting portion is designed such that a length between the two projecting portion side surfaces is smaller than a diameter of an inscribed circle defined on the insert body portion.