A coated cutting tool insert includes a substrate of cemented carbide, cermet, ceramics, steel or cubic boron nitride having deposited thereon a coating having a total thickness of 60 ?m, including one or more layers having a wear resistant layer of ?-Al.sub.2O.sub.3 of a thickness of 1 to 45 ?m deposited by chemical vapour deposition (CVD). The ?-Al.sub.2O.sub.3 layer includes at least two portions, a first thickness portion and a second thickness portion immediately on top of the first thickness portion. The first thickness portion has an essentially columnar ?-Al.sub.2O.sub.3 grain structure, and at a transition from the first thickness portion to the second thickness portion the grain boundaries of at least 1 out of 25 neighboring grains of the ?-Al.sub.2O.sub.3 grains undergo a directional change into a direction that is essentially perpendicular, 90?45 degrees, to the grain boundaries in the first thickness portion.

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.

At least a (Al.sub.1-a-b-cCr.sub.aSi.sub.bCu.sub.c)N (where 0.15a0.40, 0.05b0.20, and 0.005c0.05) layer is provided on a surface of a tool body, a Cr concentration or a Cu concentration periodically changes in a layer thickness direction, a concentration Crmax in a highest content point of Cr is in a range of a<Crmax1.3a, a concentration Crmin in a lowest content point of Cr is in a range of 0.50aCrmin<a, and optionally in a case where a Cu composition at one point z along the layer thickness direction is represented by c.sub.z and a Cr composition at the point z is represented by a.sub.z, (c.sub.z/a.sub.z)/(c/a) is 0.7 to 1.5 over the layer thickness direction entirely.

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 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.

In a drill, a negative land is provided on a rake face, and a ridge line at an intersecting position of the negative land and a flank face, a ridge line at an intersecting position of the flank face and a margin, and a ridge line at an intersecting position of the negative land and the margin are convex faces in a longitudinal rectangular cross section. When a curvature radius of the convex face of a first ridge line at the intersecting position of the flank face and the negative land is 1, at curvature radius of the convex face of a second ridge line at the intersecting position of the flank face and the margin is 0.8 to 1.5 times the curvature radius of the first ridge line, and a curvature radius of the convex face of a fourth ridge line at the intersecting position of the negative land and the margin is 1.5 to 3.0 times the curvature radius of the first ridge line.

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.

A coated tool disclosure includes a base body and a coating layer. The coating layer includes crystals having a cubic structure. The coating layer has a striped structure in cross-sectional observation by a transmission electron microscope. The striped structure has two layers alternately located in a thickness direction. The two layers contain Si and at least one metal element. The two layers each contain crystals having the cubic structure. When a lattice constant of a crystal having the cubic structure in one layer of the two layers is referred to as a first lattice constant and a lattice constant of a crystal having a cubic structure in the other layer of the two layers is referred to as a second lattice constant, a difference between a magnitude of the first lattice constant and a magnitude of the second lattice constant is greater than 0% and 0.1% or less.

Chip discharge during high-feed machining and low-feed machining particularly in a high-depth-of-cut state or the like is improved so as to provide adaptability to a wide range of cutting conditions during low depth and high depth cutting and during low-feed and high-feed machining and allow so-called freedom of feed during cutting to be improved. A cutting insert includes a cutting edge body and a substrate to which the cutting edge body is joined. The cutting edge body has a prismatic shape having a longitudinal direction and a lateral direction perpendicular to the longitudinal direction and includes a cutting edge formed on an intersecting edge between a peripheral side surface and an upper surface of the cutting edge body having the prismatic shape and a recessed part formed at a position on the upper surface of the cutting edge body which is more distant from the intersecting edge than from the cutting edge. The substrate has a projected part upwardly projecting from the upper surface of the cutting edge body.

A hard coating, which is to disposed to cover a surface of a tool substrate, has a total thickness of 0.5-20 m and includes an A layer and nanolayer-alternated layer that are alternately laminated by physical vapor deposition. The nanolayer-alternated layer includes a B layer and C layer that are alternately laminated. The A layer has a thickness of 50-1000 nm and is AlCr(SiC) nitride that is represented by a composition formula of [Al.sub.1-W-XCr.sub.W(SiC).sub.X]N wherein an atomic ratio W is 0.20-0.80 and an atomic ratio X is 0.01-0.20. The B layer has a thickness of 1-100 nm and is TiAl nitride that is represented by a composition formula of [Ti.sub.1-YAl.sub.Y]N wherein an atomic ratio Y is 0.30-0.85. The C layer has a thickness of 1-100 nm and is Ti(SiC) nitride represented by a composition formula of [Ti.sub.1-Z(SiC).sub.Z]N wherein an atomic ratio Z is 0.05-0.45. The nanolayer-alternated layer has a thickness of 50-1000 nm.