Abstract: The boundary flow path is constituted of a pair of boundary wall surfaces facing each other in a first cross section intersecting each of the first flow path, the boundary flow path, and the second flow path. An inclination of a tangent to at least one of the pair of boundary wall surfaces is continuously changed. In a second cross section perpendicular to a direction in which coolant flows, a lateral width of the first flow path is larger than a longitudinal width of the first flow path and a lateral width of the second flow path is larger than a longitudinal width of the second flow path when a longitudinal direction represents a direction in which the pair of boundary wall surfaces face each other and a lateral direction represents a direction perpendicular to the longitudinal direction.

Abstract: A cutting insert includes a cylindrical body portion, a cutting portion, a first fitting portion, a second fitting portion, and a third fitting portion. The cutting portion includes a rake face and a flank face. A ridgeline between the rake face and the flank face constitutes a cutting edge. When viewed in the axial direction, the cutting portion is provided opposite to the third fitting portion relative to the insertion hole. When viewed in the axial direction, a straight line extending through an outer circumferential end of the cutting edge and a center of the insertion hole overlaps with the third fitting portion and is located between the first fitting portion and the second fitting portion. A third central angle is smaller than a first central angle and is smaller than a second central angle.

Abstract: A cutting tool holder according to one embodiment supports a cutting insert including a rake face, a flank face, and a cutting edge. The cutting tool holder according to one embodiment includes: a holder body having a seat face on which the cutting insert is placed; a pressing member that positions and fixes the cutting insert to the holder body; and a fixing member that fixes the pressing member to the holder body. The pressing member has: a front end portion close to the cutting edge; and a base end portion distant away from the cutting edge. The front end portion is provided with a first coolant ejection hole. A first flow path is provided inside the holder body. A coolant reservoir and a second flow path are provided inside the pressing member.

Abstract: A cutting edge includes a nose portion, a first cutting edge portion, and a second cutting edge portion. When a boundary between a first inclined portion and a first breaker portion, a boundary between a first step surface and a second breaker portion, a boundary between a second inclined portion and a third breaker portion, and a boundary between a second step surface and a fourth breaker portion are a first position, a second position, a third position, and a fourth position, respectively, the second position is higher than the first position and the fourth position is higher than the third position in a direction perpendicular to the seating surface, and a distance between the first position and the third position is greater than a distance between the second position and the fourth position in a direction parallel to the seating surface.

Abstract: A cutting insert includes a cylindrical body portion, a cutting portion, a first fitting portion, a second fitting portion, and a third fitting portion. The cutting portion includes a rake face and a flank face. A ridgeline between the rake face and the flank face constitutes a cutting edge. When viewed in the axial direction, the cutting portion is provided opposite to the third fitting portion relative to the insertion hole. When viewed in the axial direction, a straight line extending through an outer circumferential end of the cutting edge and a center of the insertion hole overlaps with the third fitting portion and is located between the first fitting portion and the second fitting portion. A third central angle is smaller than a first central angle and is smaller than a second central angle.

Abstract: The upper surface includes a first breaker projection face extending along the first side surface, a second breaker projection face extending along the second side surface, and a rake face located between the first breaker projection face and the second breaker projection face in top view. In a direction from the rear surface to the front surface, a first front end of the first breaker projection face is located ahead of a second front end of the second breaker projection face. A cutting edge has a first cutting edge portion and a second cutting edge portion. In a direction perpendicular to the reference surface, the second breaker projection face is lower than the first breaker projection face, and a boundary between the first cutting edge portion and the second cutting edge portion is lower than the second breaker projection face.

Abstract: A cutting tool holder according to one embodiment supports a cutting insert including a rake face, a flank face, and a cutting edge. The cutting tool holder according to one embodiment includes: a holder body having a seat face on which the cutting insert is placed; a pressing member that positions and fixes the cutting insert to the holder body; and a fixing member that fixes the pressing member to the holder body. The pressing member has: a front end portion close to the cutting edge; and a base end portion distant away from the cutting edge. The front end portion is provided with a first coolant ejection hole. A first flow path is provided inside the holder body. A coolant reservoir and a second flow path are provided inside the pressing member.