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 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.

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.

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.

In one embodiment, a cutting tool includes an insert that includes a cutting edge at at least one part of a portion where two surfaces intersect. The cutting tool further includes a holder capable of rotating about a rotational axis. The holder includes a pocket including: a placement portion where the insert is positioned; and a cutout portion is adjacent to the placement portion and positioned further forward in a rotational direction than the placement portion. The holder further includes an inflow port that opens at at least one part of the holder, a first flow path positioned in the interior of the holder, and an outflow port positioned at the pocket. The cutout portion includes a recessed portion.

In one embodiment, a cutting tool includes an insert that includes a cutting edge at at least one part of a portion where two surfaces intersect. The cutting tool further includes a holder capable of rotating about a rotational axis. The holder includes a pocket including: a placement portion where the insert is positioned; and a cutout portion is adjacent to the placement portion and positioned further forward in a rotational direction than the placement portion. The holder further includes an inflow port that opens at at least one part of the holder, a first flow path positioned in the interior of the holder, and an outflow port positioned at the pocket. The cutout portion includes a recessed portion.

A cutter holder has a body and a damping assembly. The damping assembly is contained inside the body. The damping assembly has a central damping pole and six auxiliary damping poles. The six auxiliary damping poles are arranged around the central damping pole. The body has a specific weight. The central damping pole has a specific weight larger than the specific weight of the body. Each one of the six auxiliary damping poles has a specific weight larger than the specific weight of the body. The damping assembly is utilized to reduce vibrations caused by machining.

A cutter holder has a body and a damping assembly. The damping assembly is contained inside the body. The damping assembly has a central damping pole and six auxiliary damping poles. The six auxiliary damping poles are arranged around the central damping pole. The body has a specific weight. The central damping pole has a specific weight larger than the specific weight of the body. Each one of the six auxiliary damping poles has a specific weight larger than the specific weight of the body. The damping assembly is utilized to reduce vibrations caused by machining.

A mounting seat bottom surface facing a holder rotation direction; a first mounting seat wall surface (3b) facing an outer peripheral side of the holder main body (1), and a first relief portion (3d) on a corner portion where they intersect, are formed on an outer peripheral portion of a tip of a holder main body (1) rotated in a direction around an axis, on the inner peripheral side of the first mounting seat wall surface (3b), an inclined face (6) is formed in a range from an end edge (3b1) of the first mounting seat wall surface (3b) to 2 mm or less in the inner peripheral side, and the inclined face (6) being retracted toward the posterior end side in the axial direction as being extended toward the inner peripheral side, and an inclination angle θ is 20° or more and 50° or less.

A mounting seat bottom surface facing a holder rotation direction; a first mounting seat wall surface (3b) facing an outer peripheral side of the holder main body (1), and a first relief portion (3d) on a corner portion where they intersect, are formed on an outer peripheral portion of a tip of a holder main body (1) rotated in a direction around an axis, on the inner peripheral side of the first mounting seat wall surface (3b), an inclined face (6) is formed in a range from an end edge (3b1) of the first mounting seat wall surface (3b) to 2 mm or less in the inner peripheral side, and the inclined face (6) being retracted toward the posterior end side in the axial direction as being extended toward the inner peripheral side, and an inclination angle θ is 20° or more and 50° or less.