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 may include a base member including a plurality of tungsten carbide particles. In cases where a particle diameter distribution of the tungsten carbide particles is measured at intervals of 0.025 μm, the particle diameter distribution may include, as a maximum peak and a second peak, a first peak value that appears in a particle diameter range of 0.5-0.9 μm, and a second peak value that appears in a particle diameter range of 1.1-1.5 μm. A value of a particle diameter distribution frequency is larger than zero at a valley part where a value of the particle diameter distribution frequency reaches a minimum between the first peak value and the second peak value.

A cemented carbide may include a hard phase that may include W and C, a first solid solution phase and a second solid solution phase, each of which may include W, C, Ti and Zr, and a binder phase that may include an iron group metal. The cemented carbide may include 1.0-3.0 mass % of the Ti in terms of TiC, and 0.75-2.0 mass % of the Zr in terms of ZrC. An amount of the Ti in terms of TiC may be more than 1 time and less than three times an amount of the Zr in terms of ZrC. The first solid solution phase may satisfy a relationship of 0.1≤Ti/(Ti+Zr)<0.4 in terms of atomic ratio. The second solid solution phase satisfies a relationship of 0.7≤Ti/(Ti+Zr)≤0.9 in terms of atomic ratio.

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 rock drill insert made of cemented carbide having hard constituents of tungsten carbide (WC) in a binder phase including Co, wherein the cemented carbide includes 4-18 mass % Co and a balance of WC and unavoidable impurities. The cemented carbide also includes Cr in such an amount that the mass ratio Cr/Co is within the range of 0.04-0.19, and the difference between the hardness at a 0.3 mm depth at any point of the surface of the rock drill insert and the hardness of the bulk of the rock drill insert is at least 40 HV3.

The invention relates to a drilling tool (50), in particular a dowel hole drill, for the machining of workpieces, in particular workpieces made of wood, plastics, composite materials, comprising a drill shaft (56) with a front surface (60), and to a drill head (58) with at least one cutting edge (66), which is firmly connected, such as soldered, to the drill shaft (56). In order to make available a drilling tool of the type mentioned at the start, which has a broad range of application and is simple to produce, it is provided that the drill head (58) is formed from a composite material with exclusively two layers (38), namely a hard metal layer (36) and an ultra-hard layer (38) which is connected to the hard metal layer (36) and preferably formed from polycrystalline diamond or polycrystalline boron nitride, that the ultra-hard layer (38) is connected directly to the front surface (60) of the drill shaft (56) and that the at least one cutting edge (66) is formed by the ultra-hard layer (38), and a drill bit (62) such as a centering tip is formed by the hard metal layer (36).

Provided is a ceramic sintered body having high wear resistance and chipping resistance. Also provided are an insert, a cutting tool and a friction stir welding tool, each of which uses such a high-performance ceramic sintered body. The ceramic sintered body includes Al.sub.2O.sub.3 (alumina), WC (tungsten carbide) and ZrO.sub.2 (zirconia), wherein Zr (zirconium) element is present at either one or both of: (1) a grain boundary between crystal grains of the Al.sub.2O.sub.3; and (2) a grain boundary of crystal grains of the Al.sub.2O and crystal grains of the WC, wherein the ceramic sintered body contains 55.0 to 97.5 vol % of the WC, 0.1 to 18.0 vol % of the ZrO.sub.2, and the balance being the Al.sub.2O.sub.3, and wherein the ZrO.sub.2 is in a phase of tetragonal structure (T) or a mixed phase of tetragonal structure (T) and monoclinic structure (M).

A cutting tool made by an additive manufacturing process is disclosed. The cutting tool has an exterior surface and an enclosed interior cavity defined by one or more inwardly facing surfaces. The interior cavity may have internal supports such as a lattice or a honeycomb structure. The cutting tool may be an insert, drill or endmill with coolant holes.

When forming a first preliminary flute on a PCD layer of a columnar body, electrical discharge machining is performed by setting the electrode orientation so that the first twist angle is α. Next, when forming a second preliminary flute on a substrate of the columnar body and a round bar, the grinding process is performed by setting the grinding orientation and direction for a diamond whetstone so that a second twist angle is larger than the first twist angle.

A drill bit for chiselling rock includes an impact face at an insertion end of the drill bit, a hollow shank, where a delivery passage is defined within the hollow shank, and a drill head, where the drill head has, at a front end of the drill head, a plurality of cutting faces, an intake opening, and an intake passage. The intake passage connects the intake opening to the delivery passage. The intake opening has a noncircular cross section.