Abstract: A cutting insert includes an upper surface, a lower surface opposite to the upper surface, a first side surface and a second side surface configured to connect the upper surface and the lower surface, a mounting hole formed to penetrate the upper surface and the lower surface, a first cutting edge formed at an edge of the upper surface that meets the first side surface, and a second cutting edge formed at an edge of the upper surface that meets the second side surface. The lower surface includes a ridge portion, and a first inclined surface and a second inclined surface positioned on both sides of the ridge portion as a boundary. When looking at the lower surface, the first inclined surface and the second inclined surface have asymmetric shapes with respect to the ridge portion.

Abstract: A cutting insert has a circular top surface, a bottom surface shaped to be identical to the top surface, a cylindrical side surface for connecting the top and bottom surfaces, and cutting edges formed between the top and side surfaces and between the bottom and side surfaces. The side surface of the cutting insert has a plurality of rotation prevention surfaces substantially perpendicular to the top and bottom surfaces in the circumferential direction of the side surface.

Abstract: A cutting insert having a plurality of corner cutting edges has an upper face, a lower face, two longitudinal side faces and two transversal side faces connecting the upper face and the lower face. A through hole passes through central parts of the upper face and the lower face. The longitudinal side faces are opposite to each other and normal to both upper and lower faces, as are the transversal side faces. The upper face and the lower face are each provided with two chip discharge grooves, each chip discharge groove extending along a corresponding one of the transversal side faces, the two chip discharge grooves being inclined oppositely in the transverse direction so that the upper face and the lower face are each provided with two corner cutting edges at diagonally opposite corners. The longitudinal length of the insert is longer than the transversal length of the insert. The cutting insert can be mounted stably to a small-diametered cutter with a sufficient mounting surface.

Abstract: A cutting insert has a circular top surface, a bottom surface shaped to be identical to the top surface, a cylindrical side surface for connecting the top and bottom surfaces, and cutting edges formed between the top and side surfaces and between the bottom and side surfaces. The side surface of the cutting insert has a plurality of rotation prevention surfaces substantially perpendicular to the top and bottom surfaces in the circumferential direction of the side surface.

Abstract: A cutting insert having a plurality of corner cutting edges has an upper face, a lower face, two longitudinal side faces and two transversal side faces connecting the upper face and the lower face. A through hole passes through central parts of the upper face and the lower face. The longitudinal side faces are opposite to each other and normal to both upper and lower faces, as are the transversal side faces. The upper face and the lower face are each provided with two chip discharge grooves, each chip discharge groove extending along a corresponding one of the transversal side faces, the two chip discharge grooves being inclined oppositely in the transverse direction so that the upper face and the lower face are each provided with two corner cutting edges at diagonally opposite corners. The longitudinal length of the insert is longer than the transversal length of the insert. The cutting insert can be mounted stably to a small-diametered cutter with a sufficient mounting surface.