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 covered cutting tool having a cemented carbide and a covering layer formed on the cemented carbide. The covered cutting tool includes a rake face, a flank face, and a cutting edge line part located between the rake face and the flank face. The coating layer includes a compound layer containing a compound having a composition represented by (Al.sub.xTi.sub.1-x)N. The average thickness T.sub.1 of the covering layer in the cutting edge line part and the average thickness T.sub.2 of the coating layer in the rake face at a position 2 mm or more away from the cutting edge line part toward the rake face are within specific ranges and satisfy T.sub.2<T.sub.1. The residual stress S.sub.1 of the cemented carbide in the cutting edge line part and the residual stress S.sub.2 of the cemented carbide in the rake face at a position 2 mm or more away from the cutting edge line part toward the rake face satisfy S.sub.2<S.sub.1.

A cutting tool comprising a base material and a coating arranged on the base material; wherein: the coating comprises an α-Al.sub.2O.sub.3 layer composed of a plurality of α-Al.sub.2O.sub.3 particles; the average particle diameter a of the α-Al.sub.2O.sub.3 particles in a first region of the α-Al.sub.2O.sub.3 layer is 0.10 μm or more and 0.30 μm or less; the average particle diameter b of the α-Al.sub.2O.sub.3 particles in a second region of the α-Al.sub.2O.sub.3 layer is 0.30 μm or more and 0.50 μm or less; the average particle diameter c of the α-Al.sub.2O.sub.3 particles in a third region of the α-Al.sub.2O.sub.3 layer is 0.30 μm or more and 0.50 μm or less; and the ratio b/a is 1.5 or more and 5.0 or less.

A coated cutting tool includes a substrate and a coating. The coating has an α-Al.sub.2O.sub.3-multilayer of alternating sublayers of α-Al.sub.2O.sub.3 and sublayers of TiCO, TiCNO, AlTiCO or AlTiCNO. The α-Al.sub.2O.sub.3-multilayer includes at least 5 sublayers of α-Al.sub.2O.sub.3, wherein the total thickness of the α-Al.sub.2O.sub.3-multilayer is 1-15 μm and wherein a period in the α-Al.sub.2O.sub.3-multilayer is 50-900 nm. The α-Al.sub.2O.sub.3-multilayer exhibits an XRD diffraction over a θ-2θ scan of 20°-140°, wherein the relation of the intensity of the 0 0 12 diffraction peak (peak area), I(0 0 12), to the intensities of the 1 1 3 diffraction peak (peak area), I(1 1 3), the 1 1 6 diffraction peak (peak area), I(1 1 6), and the 0 2 4 diffraction peak (peak area), I(0 2 4), is I(0 0 12)/I(1 1 3)>1, I(0 0 12)/I(1 1 6)>1 and I(0 0 12)/I(0 2 4)>1.

A cutting blade having a plurality of different coatings on surfaces thereof, including an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, wherein the upper surface intersects the side surface to form at least one cutting edge unit, the cutting edge unit includes a main cutting edge and a secondary cutting edge, the upper surface includes at least one set of cutting planes, the cutting planes include a main cutting surface and a secondary cutting surface, the main cutting surface intersects the side surface to form the main cutting edge, the secondary cutting surface intersects the side surface to form the secondary cutting edge, a main coating is provided on the main cutting surface, a secondary coating is provided on the secondary cutting surface, and the main coating and the secondary coating are independent from each other.

A surface-coated cutting tool includes a tool body and a hard coating layer, where one TiAlCN layer α (1) containing 70 area % or more of a wurtzite type hexagonal structure on a tool surface side (S) and one TiAlCN layer β (2) containing 70 area % or more of a NaCl type face-centered cubic structure on the tool body side (B), when a composition of the TiAlCN layer α (1) is represented by (Ti.sub.(1-xα)Al.sub.xα)(C.sub.yαN.sub.(1-yα)) satisfying 0.70≤xα≤0.95 and 0.000≤yα≤0.010, when a composition of the TiAlCN layer β (2) is represented by (Ti.sub.(1-xβ)Al.sub.xβ)(C.sub.yβN.sub.(1-yβ)) satisfying 0.65≤xβ≤0.95 and 0.000≤yβ≤0.010, and when average layer thicknesses of the TiAlCN layer α (1) and the TiAlCN layer β (2) are defined as Lα and Lβ satisfying 0.5 μm≤Lα≤10.0 μm and 1.0 μm≤Lβ≤20.0 μm.

A cutting tool comprises a substrate and an AlTiN layer, the AlTiN layer including a first major surface and a second major surface, the AlTiN layer including a first region having a distance of 0 nm or more and 30 nm or less from the first major surface and having a maximum oxygen content ratio of 30 atomic % or more, a second region having a distance of more than 30 nm and 100 nm or less from the first major surface and having a maximum oxygen content ratio of 5 atomic % or more and less than 30 atomic %, and a third region having a distance exceeding 100 nm from the first major surface and having a maximum oxygen content ratio of less than 5 atomic %.

Provided is a coated cutting tool having improved wear resistance and fracture resistance and a long tool life. The coated cutting tool includes a substrate, and a coating layer formed on a surface of the substrate. The coating layer has a laminated structure in which a first layer and a second layer are alternately laminated for one or more layers. The first layer is a compound layer having a composition represented by Ti(C.sub.xN.sub.1-x). The second layer is a compound layer having a composition represented by (Ti.sub.yAl.sub.1-y)N. The laminated structure includes first to third laminated structures in this order from a substrate side to a surface side of the coating layer. An average thickness per layer of each of the first layer and the second layer in the first to third laminated structures is in a specific range. An average thickness of the first to third laminated structures is in a specific range.

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.

The drill has a rake face, a flank face, and an outer circumferential surface. The flank face is continuous to the rake face. The outer circumferential surface is continuous to both the rake face and the flank face. A ridgeline between the rake face and the flank face constitutes a cutting edge. A ridgeline between the rake face and the outer circumferential surface constitutes an outer circumferential end. A groove is provided cyclically in the rake face to extend at an angle relative to an axis of the drill, the angle being larger than a helix angle of the drill. The groove has a depth of more than or equal to 1.5 μm.