A cutting insert of a substantially horizontal cylindrical segment shape is described. The cutting insert comprises top and bottom surfaces having a circular segment shape. The cutting insert further comprises a convex side. The cutting insert further comprises a flat side. The cutting insert further comprises a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert further comprises a hole extending from the convex side towards the flat side. The hole is positioned at a center of a surface of the flat side.

A cutting insert of a substantially horizontal cylindrical segment shape is described. The cutting insert comprises top and bottom surfaces having a circular segment shape. The cutting insert further comprises a convex side. The cutting insert further comprises a flat side. The cutting insert further comprises a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert further comprises a hole extending from the convex side towards the flat side. The hole is positioned at a center of a surface of the flat side.

A cutting insert of a substantially horizontal cylindrical segment shape is described. The cutting insert comprises top and bottom surfaces having a circular segment shape. The cutting insert further comprises a convex side. The cutting insert further comprises a flat side. The cutting insert further comprises a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert further comprises a hole extending from the convex side towards the flat side. The hole is positioned at a center of a surface of the flat side.

A coated tool in the present disclosure includes a base and a coating layer located on a surface of the base. The coating layer includes an intermediate layer including Ti, and an Al.sub.2O.sub.3 layer. The Al.sub.2O.sub.3 layer is located in contact with the intermediate layer at a position further away from the base than the intermediate layer. The intermediate layer includes a plurality of first protrusions protruding toward the Al.sub.2O.sub.3 layer. An average distance between the plurality of first protrusions is 70-120 nm. A cutting tool in the present disclosure includes a holder which is extended from a first end toward a second end and includes a pocket on a side of the first end, and the coated tool located in the pocket.

A coated cutting tool is provided. The cutting tool is CVD coated and has a substrate of cemented carbide, wherein a metallic binder in the cemented carbide includes Ni. The CVD coating has an inner layer of TiN and a subsequent layer of TiCN and a layer of Al.sub.2O.sub.3 located between the TiCN layer and an outermost surface of the coated cutting tool.

A coated tool in the present disclosure includes a base and a coating layer located on a surface of the base. The coating layer includes a TiCN layer, an intermediate layer including Ti, and an Al.sub.2O.sub.3 layer in this order from a side of the base. The Al.sub.2O.sub.3 layer is located in contact with the intermediate layer at a position further away from the base than the intermediate layer. The intermediate layer includes a plurality of first protrusions protruding toward the Al.sub.2O.sub.3 layer. An average area of the plurality of first protrusions is 1700 nm.sup.2 or less. A cutting tool in the present disclosure includes a holder which is extended from a first end toward a second end and includes a pocket on a side of the first end, and the coated tool located in the pocket.

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.

A cutting insert of a substantially horizontal cylindrical segment shape may include top and bottom surfaces having a circular segment shape. The cutting insert may include a convex side and a flat side. The cutting insert may include a top cutting edge which is formed where the convex side and the top surface meet, and a bottom cutting edge which is formed where the convex side and the bottom surface meet. The cutting insert may include a hole extending from the convex side towards the flat side. The hole may be positioned at a center of a surface of the flat side.

A coated cutting tool comprising a substrate containing a cubic boron nitride-containing sintered body, and a coating layer formed on the substrate, wherein the coating layer comprises a lowermost layer and an alternating laminate structure in this order, the lowermost layer comprises (Al.sub.1-xCr.sub.x)N, an average thickness of the lowermost layer is 0.01 μm or more and 0.2 μm or less, the alternating laminate structure includes mutually different two kinds of compound layers of a first compound layer containing (Al.sub.1-y1Cr.sub.y1)N and a second compound layer containing (Al.sub.1-y2Cr.sub.y2)N alternately laminated repeatedly twice or more, an average thickness of the entire alternating laminate structure is 0.1 μm or more and 1.2 μm or less, an average thickness of the entire coating layer is 0.2 μm or more and 1.3 μm or less, and a compressive residual stress at the cubic crystal (111) plane is 3.0 GPa or less.

A cemented carbide includes first hard phase grains, second hard phase grains, third hard phase grains, and a metal binder phase, wherein the cemented carbide has a total of 70 unit regions, the number of unit regions each having a percentage of less than 0.43% or more than 2.43% is ≤10 among the total of 70 unit regions, the percentage being a percentage of the total number of the second and the third hard phase grains in each unit region with respect to the total number of the second and the third hard phase grains in the total of 70 unit regions, and in a total of 10 unit regions existing in a fourth row in a longitudinal direction, a percentage of the number of the third hard phase grains with respect to the total number of the second and the third hard phase grains is 5% to 15%.