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.

The flow of heat energy from the cutting edge rim of a self-propelled round annular rotary cutting element (insert) to axial-load and radial-load bearings in a cartridge which rotatably supports the insert on a machine tool body is reduced by defining heat flow paths from the insert rim to cartridge components which engages the bearings to have low thermal conductance relative to heat flow paths from the insert rim to other parts of the cartridge. Control over heat flow path thermal conductance is obtained by selection of materials used between the insert rim and the mentioned cartridge components, by reductions in the cross-sectional areas of the critical heat flow paths, and by combinations of those two techniques. Protection of the bearings from heat enables the insert and the cartridge to be reduced in size. Improved mountings of insert-supportive cartridges to tool bodies are disclosed. The insert and the cartridge preferably are shaped to enable the insert to be positioned on a tool body so that the insert's rake face can have a positive rake orientation relative to a workpiece. Arrangements for controlling cuttings chip formation and for handling cuttings chips also are disclosed.

A cutting insert based on a non-limiting aspect has a first member and a second member joined to the first member. The second member has an upper surface and a side surface adjacent to the upper surface. The upper surface includes a first side, a second side and a corner. The upper surface has a first convex portion extending toward the corner, and a second convex portion extending from the first convex portion toward the first side. The second convex portion has a first end portion and a second end portion located closer to the corner than the first end portion. A first length from the first end to the first side is less than a second length from the second end portion to the first side in a top view.

A coating for carbide substrates employs a nanostructured coating in conjunction with a non-nanostructured coating. The nanostructured coating is produced by the addition of a refining agent flow, particular hydrogen chloride gas, during deposition, and may be produced as multiple individual titanium and titanium-based nanostructured layers varying functional materials in a series. The combination of a nanostructured coating and non-nanostructured coating is believed to produce a cutting tool insert that exhibits longer life. Pre-treating the substrate with a mixture of compressed air and abrasive medium prior to coating the substrate and post-treating the coated substrate with a mixture of water and abrasive medium after the coating process is believed to further enhance the wear resistance and usage life of the cutting tool.

A coated tool includes a base and a coating layer located on the base. The coating layer includes a first layer having a thickness of 1 m or more located near the base, and a second layer including Al.sub.2O.sub.3 particles which is in contact with the first layer and is located more away from the base than the first layer. A difference (A2A1) between an erosion ratio A2 in the second layer and an erosion ratio A1 in the first layer is 0.60 to 0.30 m/g. The erosion ratio is obtained by collision of a liquid A in which 3 mass % of spherical Al.sub.2O.sub.3 particles having a mean particle diameter of 1.1-1.3 m is dispersed in pure water. A cutting tool includes a holder which includes a pocket, and the coated tool located in the pocket.

For providing a structural material having improved fatigue strength and abrasion resistance, provided is a structural material containing iron and carbon, including: a first layer formed of pearlite; a second layer formed of a mixed phase of martensite and a carbide; and a third layer formed of a carbide, in order from a center to a surface of the structural material. The carbide of the third layer is represented by MC (where M is one element among Ti, V, Nb, Mo, Ta, and W), and the structural material has a concentration gradient in which an M element concentration is decreased from the surface to the center of the structural material.

A coated cutting tool according to the present invention is a coated cutting tool comprising a substrate and a coating layer formed on a surface of the substrate, wherein: the coating layer comprises a lower layer, an intermediate layer formed on a surface of the lower layer, and an upper layer formed on a surface of the intermediate layer; the lower layer is a predetermined Ti compound layer with a predetermined average thickness; the intermediate layer is an -type aluminum oxide layer with a predetermined average thickness; the upper layer is a Ti carbonitride layer with a predetermined average thickness; and a texture coefficient of a predetermined plane of each of the -type aluminum oxide layer and the Ti carbonitride layer falls within a predetermined range.

A cemented carbide comprising a predetermined hard phase, a predetermined binder phase and a predetermined composite compound phase, wherein: a content ratio of each of the hard phase, the binder phase and the composite compound phase based on total contents of the hard phase, the binder phase and the composite compound phase in the cemented carbide falls within a predetermined range; and the composite compound phase comprises an aggregate containing a small-diameter aggregate which satisfies a predetermined condition and a large-diameter aggregate which satisfies a predetermined condition.

A surface coated cutting tool comprises a tool body. A TiAlCN layer having an average layer thickness of 2.0 to 20.0 ?m and represented by (Ti.sub.(1-x)Al.sub.x)(C.sub.yN.sub.(1-y)) is provided on the surface of the tool body and has an average content ratio x.sub.avg of Al and an average content ratio y.sub.avg of C that satisfy 0.60?x.sub.avg?0.95 and 0.00?y.sub.avg?0.05, an area ratio occupied by crystal grains having an NaCl-type face-centered cubic structure that satisfies 90 area % or more, and crystal grains satisfying 0.01 ?m<d?0.20 ?m in 10 to 40 area %. An average maximum length in a direction parallel to the surface of the tool body in each region in which the crystal grains having d of 0.01 ?m<d?0.20 ?m are adjacent and connected to each other in the upper layer side region is 5.0 ?m or less.

A cutting tool according to one aspect of the present disclosure includes an attaching portion, a cutting portion having a core portion and a surface portion, and a joint portion. The attaching portion includes a hard component and a hard material. The hard component is at least one selected from the group consisting of TiC, TiCN, W, WC, Al.sub.2O.sub.3, and a combination of at least one of CBN and diamond and at least one of W and WC. The hard material includes one or two or more types of iron group elements, and has a Young's modulus of not more than 350 GPa. The core portion includes a cemented carbide material. The surface portion includes PCD or CBN. The cutting portion has a chamfer portion. The surface portion includes a groove, a flank face, and a cutting edge. The cutting edge extends toward the attaching portion.