A cutting insert suitable for a small-diameter milling tool is provided. A cutting insert has a rake face, a bottom surface, a circumferential side surface, and a through hole. A first ridgeline at which the rake face and the circumferential side surface intersect each other includes a first main cutting edge, and a first corner cutting edge connected to a tip of the first main cutting edge. The bottom surface includes a first bottom surface that comes closer to the rake face gradually toward a side at which the first main cutting edge is located when viewed from a central axis of the through hole, and a second bottom surface that comes closer to the rake face gradually toward a side opposite to the first main cutting edge when viewed from the central axis. A distance between a virtual intersection line, at which a first virtual surface formed by extending the first bottom surface and a second virtual surface formed by extending the second bottom surface intersect each other, and the first main cutting edge decreases from a tip side, at which the tip of the first main cutting edge is located, toward an end side, at which an end opposite to the tip is located, in an extending direction of the first main cutting edge.

A metal slitter body including a cylindrical body portion and cutting body portions extending outwardly from and integrally formed with the cylindrical body portion. The cutting body portions each include an insert pocket having an insert receiving slot, first and second clamping jaws and a slot end. The slitter body further including a reinforcement portion extending from the cylindrical body in an outward radial direction further than each slot end.

A metal slitter body including a cylindrical body portion and cutting body portions extending outwardly from and integrally formed with the cylindrical body portion. The cutting body portions each include an insert pocket having an insert receiving slot, first and second clamping jaws and a slot end. The slitter body further including a reinforcement portion extending from the cylindrical body in an outward radial direction further than each slot end.

An indexable cutting insert has opposing upper and lower end surfaces, and a peripheral surface including three side surfaces and three corner surfaces. Each corner surface intersects the upper end surface to form an upper cutting edge, and each side surface has a locating surface. The lower end surface has three radially outward facing lower abutment surfaces. The three locating surfaces define a first imaginary triangle having three first bisector planes and three locating planes, and the three lower abutment surfaces define a second imaginary triangle having three second bisector planes. None of the first and second bisector planes are coplanar, and each locating plane intersects two of the upper cutting edges. For each index position of the cutting insert in an insert receiving pocket of a cutting tool, one of the locating surfaces and one of the lower abutment surfaces is in contact with pocket walls thereof.

A coated tool includes a base body and a diamond coating. The coated tool has a cutting edge. The first surface comprises a first region close to the cutting edge and a second region further away from the cutting edge than the first region. The diamond coating comprises an outer surface having dome-shaped protrusions. The protrusions include first protrusions having an equivalent circle diameter of 6 .Math.m or more located in the first region, and second protrusions having an equivalent circle diameter of 6 .Math.m or more located in the second region. A number of the first protrusions per 1 mm.sup.2 is a first protrusion number. A number of the second protrusions per 1 mm.sup.2 is a second protrusion number. The first protrusion number is 30 or less, and the second protrusion number is larger than the first protrusion number.

A coated tool includes a base body and a diamond coating. The coated tool has a cutting edge. The first surface comprises a first region close to the cutting edge and a second region further away from the cutting edge than the first region. The diamond coating comprises an outer surface having dome-shaped protrusions. The protrusions include first protrusions having an equivalent circle diameter of 6 .Math.m or more located in the first region, and second protrusions having an equivalent circle diameter of 6 .Math.m or more located in the second region. A number of the first protrusions per 1 mm.sup.2 is a first protrusion number. A number of the second protrusions per 1 mm.sup.2 is a second protrusion number. The first protrusion number is 30 or less, and the second protrusion number is larger than the first protrusion number.

A milling tool cutter includes a tool body, a plurality of cutting inserts, a plurality of clamping studs, a clamping ring, and a detachable fastening member. The tool body has a plurality of pockets disposed circumferentially around the tool body. Each of the cutting inserts is disposed in one of the respective pockets. Each of the clamping studs is attached to one of the respective cutting inserts. The clamping ring is disposed within the tool body. The clamping ring includes a face surface, a seating surface, and a circumferential outer surface extending between the face surface and the seating surface. The seating surface sits against the plurality of clamping studs. The detachable fastening member is disposed in an attached state fixedly attaching the clamping ring to the tool body causing the clamping studs and their respective cutting inserts to be fixedly attached to the tool body.

A cutting insert adaptor for an insert pocket can include one or more pairs of opposing insert abutment surfaces and pocket abutment surfaces which converge at an acute angle. The one or more insert abutment surfaces are all rotated in the same direction, relative to their paired pocket abutment surface which in turn rotates a cutting insert abutting the cutting insert adaptor relative to an orientation the cutting insert would have if it only abutted the insert pocket instead of the cutting insert adaptor.

A cutting insert adaptor for an insert pocket can include one or more pairs of opposing insert abutment surfaces and pocket abutment surfaces which converge at an acute angle. The one or more insert abutment surfaces are all rotated in the same direction, relative to their paired pocket abutment surface which in turn rotates a cutting insert abutting the cutting insert adaptor relative to an orientation the cutting insert would have if it only abutted the insert pocket instead of the cutting insert adaptor.

A cutting insert in a non-limiting aspect of the present disclosure may include an upper surface having a polygonal shape and including a first side, a lower surface, and a lateral surface. The lateral surface may include a first lateral surface located between the first side and the lower surface. The first lateral surface may include a first region that is flat. The first region may include a first central region, a first upper region and a first lower region. The first upper region may be located closer to the upper surface than the first central region, and may have a larger width than the first central region. The first lower region may be located closer to the lower surface than the first central region, and may be a larger width than the first central region.