The present invention is directed to a surface-coated cubic boron nitride sintered material tool including a cBN substrate and a hard coating layer formed on a surface of the cBN substrate and having an alternate laminated structure of A layer and B layer. A peak of the grain size distribution of cBN grains in the cBN sintered material is present within a range of a grain size from 0.50 to 1.00 m. The A layer has a composition of (Ti.sub.1-xAl.sub.x)N (0.4x0.7 in an atomic ratio). The B layer has a composition of (Cr.sub.1-y-zAl.sub.yM.sub.z)N (0.03y0.6 and 0z0.05 in an atomic ratio). An X-ray diffraction peak of a (200) plane is present at a position of a diffraction angle of 43.6 plus or minus 0.1 degrees, and a plastic deformation work ratio of the B layer is 0.35 to 0.50.

In an embodiment, a cutting insert includes an upper surface, a one or more side surfaces, and a cutting edge. The upper surface includes a first corner portion, and a first side that is adjacent to the first corner portion. The side surfaces are adjacent to the upper surface. The cutting edge is disposed on at least a portion of a section where the upper surface and the side surfaces intersect. The cutting edge includes first, second, third and fourth cutting edges. The first cutting edge is disposed at the first corner portion and has a convex curved shape. The second cutting edge is next to the first cutting edge, and has a linear shape. The third cutting edge is next to the second cutting edge, and has a convex curved shape. The fourth cutting edge is next to the third cutting edge on the first side.

A drill in which: a chip discharge groove is formed in an outer periphery of an edge portion serving as a leading end side portion of a drill body; and a cutting edge is formed in an intersecting edge between a rake surface of a leading end side region and a leading end flank of the edge portion, the drill comprising a margin portion, a shoulder portion and a web thinning portion, wherein: the cutting edge comprises, in order from a rotation center, a first cutting edge portion, a second cutting edge portion, a shoulder cutting edge portion, and a margin cutting edge portion; the honing width gradually decreases from the boundary P1 toward the position P2; and the conditions represented by expression (1): honing width of second cutting edge portion?R1 and expression (2): 2.0<R1/R2<5.0 are satisfied.

An insert based on an aspect includes a first surface having a corner portion, a second surface, a third surface, and a cutting edge located on at least part of a portion on which the first surface and the third surface intersect. The cutting edge is provided with a first cutting edge located on the corner portion and a second cutting edge adjacent to the first cutting edge, and the third surface is provided with a first portion located along the first cutting edge and a second portion located along the second cutting edge. Additionally, the second portion includes a first region having a first end portion and a second end portion, and a second region having a third end portion and a fourth end portion. An inclination angle 212 at the second end portion is greater than an inclination angle 211 at the first end portion, and an inclination angle 222 at the fourth end portion is smaller than an inclination angle 221 at the third end portion.

A coated cutting tool comprising a substrate and a coating layer formed on a surface of the substrate, wherein: the coating layer comprises at least one -type aluminum oxide layer; and, in the -type aluminum oxide layer, when regarding a texture coefficient of a (0,0,6) plane as a TC18 (0,0,6), and also regarding a texture coefficient of a (0,0,12) plane as a TC18 (0,0,12), the TC18 (0,0,6) is the highest texture coefficient and the TC18 (0,0,12) is the second highest texture coefficient.

A surface-coated cutting tool includes a substrate composed of cemented carbide and a coating film. The coating film includes an intermediate layer in contact with the substrate and an upper layer formed on the intermediate layer. The upper layer is made up of a single layer consisting of an upper base layer which is a layer in contact with the intermediate layer or multiple layers constituted of two or more layers. A mismatch in lattice interplanar spacing in an interface region between the substrate and the intermediate layer is not higher than 65% of a theoretical value of a mismatch in lattice interplanar spacing between the substrate and the upper base layer. A mismatch in lattice interplanar spacing in an interface region between the intermediate layer and the upper base layer is not higher than 65% of the theoretical value of the mismatch in lattice interplanar spacing between the substrate and the upper base layer.

The present disclosure relates to a cutting tool of a cemented carbide substrate including WC and a binder phase having one or more of Co, Fe and Ni, wherein the cemented carbide also includes a finely dispersed eta phase of Me12C and/or Me6C carbides, where Me is one or more metals selected from W, Mo and the binder phase metals, wherein the substoichiometric carbon content in the cemented carbide is between 0.30 to 0.16 wt %. The disclosed cutting tool will achieve an improved resistance against comb cracks.

A coated cutting tool is provided which has improved wear resistance and fracture resistance and which accordingly has a long tool life. A coated cutting tool comprising a substrate and a coating layer formed on the substrate, wherein: the coating layer comprises at least one composite compound layer containing a compound having a composition represented by (Ti.sub.1-xMo.sub.x)N (wherein x denotes an atomic ratio of the Mo element based on a total of the Ti element and the Mo element and satisfies 0.01?x?0.30); a ratio I(200)/I(111) between a peak intensity I(111) for a (111) plane of cubic crystals of the composite compound layer and a peak intensity I(200) for a (200) plane of the cubic crystals in an X-ray diffraction analysis satisfies 1<I(200)/I(111)?20; and, as to particles which constitute the composite compound layer, an area ratio of particles each having an aspect ratio of 2 or more is 50% or higher.

A cutting insert according to an aspect includes a top surface and a side surface. At least a part of a ridge line where the top surface and the side surface intersects is a cutting edge. The cutting edge includes a first portion located at a corner portion, a second portion adjacent to the first portion, a third portion close to the second portion, a fourth portion close to the third portion, and a fifth portion adjacent to the fourth portion. When viewed from directly above, a curvature radius of the second portion is less than a curvature radius of the first portion, a curvature radius of the third portion is greater than the curvature radius of the first portion, and a curvature radius of the fourth portion is less than the curvature radius of the third portion.

Problem: To provide a cutting tool formed from a silicon nitride-based sintered body having high fracture resistance and having residual stress of a rake face and a flank face in an appropriate range. Solution: A cutting tool (1) formed from a silicon nitride-based sintered body containing not less than 50 volume % silicon nitride-based phase and from 10 to 30 volume % titanium nitride phase, uses an intersection ridge portion of a rake face (2) and a flank face (3) as a cutting edge (4), has a residual stress applied to the titanium nitride phase that is tensile stress, and is such that the tensile stress applied to the titanium nitride phase in the rake face (2) is greater than the tensile stress applied to the titanium nitride phase in the flank face (3).