A reversible cutting insert for milling including opposing and identically or substantially identically top and bottom surfaces interconnected by a continuous peripheral side surface, with a median plane located between the top and bottom surfaces and intersecting the side surface, and an insert axis perpendicular to the median plane about which the cutting insert is indexable. Each top and bottom surface is limited by a circumferential cutting edge intersecting the side surface, the circumferential cutting edge in a top view having the shape of a truncated equilateral triangle. Each circumferential cutting edge includes three analogous sets of cutting edges exhibiting three-fold rotational symmetry about the insert axis. A first cutting edge portion intersects a first support plane.

What is presented is a cutting insert including a polygonal plate-shaped insert main body that includes: two polygonal surfaces; a side surface; and a cutting edge, the insert main body has a mounting hole that is centered on an insert center line passing through centers of the two polygonal surfaces, the cutting edge includes a major cutting edge extending from a first end of a corner edge located at a corner of the polygonal surface, and, in the opening of the mounting hole, a plurality of protrusions protruding with respect to a boss surface around an opening of the mounting hole are formed at intervals in a peripheral direction in an inner periphery side region of the major cutting edge.

A cutting tool according to an aspect of the present disclosure includes a cutting edge portion which contains at least one of cubic boron nitride and polycrystalline diamond. The cutting edge portion includes a flank face, a negative land contiguous to the flank face, and a cutting edge formed by a ridgeline between the flank face and the negative land. At least one of the negative land and the flank face is provided with a plurality of recesses and a projection. The projection is formed by arranging the edges of adjacent recesses in contact with each other.

The technical objective of the present invention is to provide a cutting insert that has an improved fastening property with a cutting tool, thereby preventing reduction of the service life. To this end, the cutting insert according to the present invention has three corners along the circumference thereof; an upper main cutting edge, which is formed on the edge between the upper surface and the first side surface, and an upper sub cutting edge, which is formed on the edge between the upper surface and the second side surface, are continuously disposed between respective corners; the lower surface has the same shape as that of the upper surface; and the angle defined between the upper main cutting edge and the upper sub cutting edge, which are placed on both sides with reference to each corner, is larger than or equal to 85? and is smaller than 90?.

A reversible cutting insert for milling including opposing and identically or substantially identically top and bottom surfaces interconnected by a continuous peripheral side surface, with a median plane located between the top and bottom surfaces and intersecting the side surface, and an insert axis perpendicular to the median plane about which the cutting insert is indexable. Each top and bottom surface is limited by a circumferential cutting edge intersecting the side surface, the circumferential cutting edge in a top view having the shape of a truncated equilateral triangle. Each circumferential cutting edge includes three analogous sets of cutting edges exhibiting three-fold rotational symmetry about the insert axis. A first cutting edge portion intersects a first support plane.

A cutting tool according to an aspect of the present disclosure includes a cutting edge portion which contains at least one of cubic boron nitride and polycrystalline diamond. The cutting edge portion includes a flank face, a negative land contiguous to the flank face, and a cutting edge formed by a ridgeline between the flank face and the negative land. At least one of the negative land and the flank face is provided with a plurality of recesses and a projection. The projection is formed by arranging the edges of adjacent recesses in contact with each other.

The technical objective of the present invention is to provide a cutting insert that has an improved fastening property with a cutting tool, thereby preventing reduction of the service life. To this end, the cutting insert according to the present invention has three corners along the circumference thereof; an upper main cutting edge, which is formed on the edge between the upper surface and the first side surface, and an upper sub cutting edge, which is formed on the edge between the upper surface and the second side surface, are continuously disposed between respective corners; the lower surface has the same shape as that of the upper surface; and the angle defined between the upper main cutting edge and the upper sub cutting edge, which are placed on both sides with reference to each corner, is larger than or equal to 85? and is smaller than 90?.