A cutting insert includes an upper surface, a lower surface opposite to the upper surface, a first side surface and a second side surface configured to connect the upper surface and the lower surface, a mounting hole formed to penetrate the upper surface and the lower surface, a first cutting edge formed at an edge of the upper surface that meets the first side surface, and a second cutting edge formed at an edge of the upper surface that meets the second side surface. The lower surface includes a ridge portion, and a first inclined surface and a second inclined surface positioned on both sides of the ridge portion as a boundary. When looking at the lower surface, the first inclined surface and the second inclined surface have asymmetric shapes with respect to the ridge portion.

Provided is a method of manufacturing an elbow, including: a first cutting step of cutting a material by relatively moving a cutting section of a cutting tool, which is formed of at least a part of a substantially spherical shape, along an inner side surface of the elbow to be finished in a direction from a first end surface to a second end surface of the material; and a second cutting step of cutting the material by relatively moving the cutting section along the inner side surface of the elbow to be finished in a direction from the second end surface to the first end surface of the material.

Large diameter edges formed in arc shapes having curvature radii larger than a ball radius are provided. This allows improving surface roughness of a machined surface by cutting of a planar surface with the respective large diameter edges compared with cutting of a planar surface with a ball end cutting edge formed in an arc shape having a single curvature radius. Further, since the respective large diameter edges are formed in the arc shape, compared with cutting of a curved surface with linear cutting edges, surface roughness of a machined surface can be improved by cutting a curved surface with the respective large diameter edges. Accordingly, a pick feed during the cutting of the planar surface and the curved surface with the respective large diameter edges can be increased, and therefore machining efficiency in the cutting of both of the planar surface and the curved surface can be improved.

The invention relates to a ball track milling cutter (1), comprising a carrier body (2) and at least one cutting element (3) having a cutting edge (31), the carrier body (2) comprising at least one recess (21) for partly receiving the cutting element (3), and the recess (21) being designed to receive a reground cutting element (3) having a reground shape and size.

The present invention relates to a cutting tool, which performs, like a drill or a ball end mill, cutting while rotating in a state in which the center of the tip end is in contact with a work material, and includes a wear-resistant layer formed at the tip end thereof, wherein a portion of the wear-resistant layer is selectively removed through tip end polishing from the center of the tip end of the drill or the ball end mill to a predetermined area, so as to restrain micro-brittle wear generated in an ultra-low speed region, and thus remarkably improving the cutting lifespan of the cutting tool such as the drill or the ball end mill.

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.

This cutting insert has: as cutting edges, arcuate cutting edges that are of an arc shape protruding toward an outer circumference side of a distal end. A chisel part is formed at an intersecting ridge line part between the flank faces of the pair of arcuate cutting edges. A round honing is formed on the cutting edge tip of the arcuate cutting edge at least in a range where a radial angle is 30 or less. A curvature radius of the round honing in a cross section perpendicular to the edge length direction of the arcuate cutting edge is 20 to 40 m. A chisel angle formed between the distal end part of the arcuate cutting edge and a chisel edge of the chisel part is 150 to 170 as seen in an insert front view.

The present invention relates to a cutting tool, which performs, like a drill or a ball end mill, cutting while rotating in a state in which the center of the tip end is in contact with a work material, and includes a wear-resistant layer formed at the tip end thereof, wherein a portion of the wear-resistant layer is selectively removed through tip end polishing from the center of the tip end of the drill or the ball end mill to a predetermined area, so as to restrain micro-brittle wear generated in an ultra-low speed region, and thus remarkably improving the cutting lifespan of the cutting tool such as the drill or the ball end mill.

This cutting insert has: as cutting edges, arcuate cutting edges that are of an arc shape protruding toward an outer circumference side of a distal end. A chisel part is formed at an intersecting ridge line part between the flank faces of the pair of arcuate cutting edges. A round honing is formed on the cutting edge tip of the arcuate cutting edge at least in a range where a radial angle is 30 or less. A curvature radius of the round honing in a cross section perpendicular to the edge length direction of the arcuate cutting edge is 20 to 40 m. A chisel angle formed between the distal end part of the arcuate cutting edge and a chisel edge of the chisel part is 150 to 170 as seen in an insert front view.

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.