A cutting insert in a non-limiting embodiment may include a first surface, a second surface, a third surface and a land surface. The first surface may include a first corner and a first side extended from the first corner. The land surface may be located between the first surface and the third surface and inclined relative to the first surface and the third surface. The land surface may include a first land surface located along the first corner, a second land surface located along the first side, and a third land surface having a concave shape which is adjacent to the second land surface and located further away from the first land surface than the second land surface.

A rotary cutting tool is provided which, although it has a simple configuration, allows the arrangement of each cutting edge to be easily adjusted. A first cartridge mounting seat has an upper wall surface opposing an outer side surface of a cartridge and further has a first recessed part into which a protrusion is inserted and which comes into contact, at a bottom thereof, with a leading end of the protrusion. A second cartridge mounting seat has an upper wall surface opposing an outer side surface of a cartridge and further has a second recessed part into which a protrusion is inserted and which comes into contact, at a bottom thereof, with a leading end of the protrusion. A depth of the second recessed part is greater than a depth of the first recessed part. An amount of protrusion P of the protrusion is equal to or greater than the depth of the second recessed part.

A cutting insert includes an upper surface and a cutting edge. The upper surface includes a first surface and a second surface which is located further inward than the first surface. The cutting edge includes a first cutting edge and a second cutting edge. The first surface includes a first region along the first cutting edge, a second region adjacent to the first region, and a third region which is adjacent to the second region and along the second cutting edge. The second surface includes a fourth region, a fifth region and a sixth region. A width of the second region is smaller than each of a width of the first region and a width of the third region. An inclination angle of the fifth region is smaller than each of an inclination angle of the fourth region and an inclination angle of the sixth region.

A cutting insert including a surface involved in cutting, for which a cutting tool material of a hard sintered body is used. A radius of a nose R portion is 0.4 mm or greater and 2.4 mm or less, an apex angle of the nose R portion is 50 or greater and 95 or less, a rake angle at a position of a bisecting plane of the apex angle of the nose R portion is 1 or greater and 10 or less, a chamfer provided in a cutting edge portion is a negative land with unequal width, and at least on one side of the negative land with respect to a boundary which is an apex of a nose R portion cutting edge, a width of the negative land gradually decreases from the apex of the nose R portion cutting edge to a position at which the nose R portion cutting edge is connected to a linear cutting edge. Let W1 be the width of the negative land at the apex of the nose R portion cutting edge, and W2 be the width of the negative land at both ends of the nose R portion cutting edge, then the W1 is 0.04 mm or greater and 0.2 mm or less, and a ratio of the W1 to the W2 is 1.5 or greater.

A cutting insert of one aspect is provided with a top surface having a polygonal shape and including a corner portion, a first side and a second side, each extending from the corner portion, a bottom surface, a side surface, and a cutting edge. The cutting edge includes a corner cutting edge disposed in a position corresponding to the corner portion, and a first cutting edge disposed in a position corresponding to the first side. The top surface includes an inclined surface provided with a first inclined surface disposed along the first side, a second inclined surface disposed along the second side, and a third inclined surface disposed along the corner portion. An inclination angle of the first inclined surface is greater than an inclination angle of the second inclined surface.

A cutting insert of an embodiment includes a cutting edge located at an intersecting part of an upper surface and a side surface. The cutting edge includes a corner cutting edge, a major cutting edge, and a flat cutting edge. The upper surface includes a first land surface located along the corner cutting edge, a second land surface located along the major cutting edge, and a third land surface located along the flat cutting edge. A maximum value of a width of the third land surface is smaller than a maximum value of a width of each of the first land surface and the second land surface in a top view.

A cutting insert (1) has a first end surface (2); a second end surface (3) opposing the first end surface; and a peripheral side surface (4) connecting the first and second end surfaces. A cutting edge (6) extends along an intersecting edge between the first end surface and the peripheral side surface. A land (20) is formed in the first end surface and extends along the cutting edge. At least one groove (18) is formed in the peripheral side surface, each groove forming an opening in the first end surface and separating the cutting edge into a plurality of portions. In a plan view of the first end surface, a portion of the land adjacent to an end area (S) of the groove, has a greater width than a width of a portion of the land which is distant from the groove.

A rotary cutting tool is provided which, although it has a simple configuration, allows the arrangement of each cutting edge to be easily adjusted. A first cartridge mounting seat has an upper wall surface opposing an outer side surface of a cartridge and further has a first recessed part into which a protrusion is inserted and which comes into contact, at a bottom thereof, with a leading end of the protrusion. A second cartridge mounting seat has an upper wall surface opposing an outer side surface of a cartridge and further has a second recessed part into which a protrusion is inserted and which comes into contact, at a bottom thereof, with a leading end of the protrusion. A depth of the second recessed part is greater than a depth of the first recessed part. An amount of protrusion P of the protrusion is equal to or greater than the depth of the second recessed part.

A cutting insert includes a rake face, a flank face, a cutting edge formed at a ridge where the rake face and the flank face intersect, a land provided on the rake face along the cutting edge, a breaker groove provided in the rake face inside of the land, and a curved surface formed between a groove surface of the breaker groove and the land. A radius of curvature of the curved surface is 0.5 mm or greater.