An object of the present disclosure is to improve the properties of a ceramic composition. A ceramic composition contains alumina (Al.sub.2O.sub.3) and tungsten carbide (WC) and is characterized in that an atomic layer formed of at least one element selected from among transition metals belonging to Groups 4 to 6 of the periodic table, yttrium (Y), scandium (Sc), and lanthanoids is present at a crystal grain boundary between an alumina (Al.sub.2O.sub.3) crystal grain and a tungsten carbide (WC) crystal grain.

A multilayer hard film-coated cutting tool including a cutting tool body and a multilayer hard film formed on a surface of the cutting tool body, wherein the multilayer hard film comprises at least an upper layer and a lower layer; the upper layer is made of a Ti and Si compound layer; the lower layer is made of a multi-layered film of an A-layer and a B-layer, a layer thickness of the B-layer is equal to or thicker than a layer thickness of the A-layer, a ratio of the layer thicknesses of the A-layer and the B-layer being A-layer:B-layer=1:1 to 1:2, the multilayer hard films having 2 to 8 pairs of the A-layer and the B-layer in a case where a single pair is defined by a combination of a single A-layer and a single B-layer.

A surface-coated cutting tool includes a base material and a coating formed on a surface of the base material. The coating includes a first hard coating layer including crystal grains having a sodium chloride-type crystal structure. The crystal grain has a layered structure in which a first layer composed of nitride or carbonitride of Al.sub.xTi.sub.1x and a second layer composed of nitride or carbonitride of Al.sub.yTi.sub.1y are stacked alternately into one or more layers. The first layer each has an atomic ratio x of Al varying in a range of 0.76 or more to less than 1. The second layer each has an atomic ratio y of Al varying in a range of 0.45 or more to less than 0.76. The largest value of difference between the atomic ratio x and the atomic ratio y is 0.05xy0.5.

A drill bit has, along a drill bit axis, a drilling head, a multi-start helix made of two or more helical coils, and an insertion end. The helix has a helix slope and a pitch in a delivery region. In an outlet region of the helix, the outlet region being directed towards the insertion end, the helical coils merge continuously, within a first portion, from an orientation in alignment with the helix slope into an orientation parallel to the drill bit axis. A length of the first portion is at least one quarter of the pitch of the delivery region. The helical coils, in a second portion, are oriented parallel to the drill bit axis.

A surface-coated cutting tool includes a base material and a coating formed on a surface of the base material. The coating includes a first hard coating layer including crystal grains having a sodium chloride-type crystal structure. The crystal grain has a layered structure in which a first layer composed of nitride or carbonitride of Al.sub.xTi.sub.1-x and a second layer composed of nitride or carbonitride of Al.sub.yTi.sub.1-y are stacked alternately into one or more layers. The first layer each has an atomic ratio x of Al varying in a range of 0.76 or more to less than 1. The second layer each has an atomic ratio y of Al varying in a range of 0.45 or more to less than 0.76. The largest value of difference between the atomic ratio x and the atomic ratio y is 0.05x-y0.5.

A surface-coated tool includes a substrate and a coating film formed on the substrate. The coating film includes an alternate layer in which one or more A layers and one or more B layers are alternately stacked. The A layer and the B layer each have a thickness not smaller than 2 nm and not greater than 100 nm. An average composition of the A layer is expressed as TiaAlbSicN (0.5<a<0.8, 0.2<b<0.4, 0.01<c<0.1, a+b+c=1), an average composition of the B layer is expressed as TidAleSifN (0.4<d<0.6, 0.3<e<0.7, 0.01<f<0.1, d+e+f=1), and a condition of 0.05<AD0.2 AND 0.05<EB0.2 is satisfied.

The present invention relates to a coated cutting tool including a substrate and a coating. The coating has, from about 0.5 to about 10 m, a nano-multilayer of alternating nanolayers of a first nanolayer type of Ti.sub.1-xAl.sub.xN, wherein 0.45x<0.67, a second nanolayer type of Cr.sub.1-yAl.sub.yN, wherein 0.60y0.80, and a third nanolayer type of Ti.sub.1-zSi.sub.zN, wherein 0.14z0.25. An average nanolayer thickness of each of the nanolayer types Ti.sub.1-xAl.sub.xN, Cr.sub.1-yAl.sub.yN and Ti.sub.1-zSi.sub.zN in the nano-multilayer is 1 nm but <3 nm.

One aspect of the disclosure relates to a cutting tool for forming a final opening in a stack that includes at least two layers and a pilot opening having a pilot-opening dimension and extending through at least one of the at least two layers. The cutting tool includes a shank. The cutting tool also includes a first portion including at least one of a first coating or the first coating and a second coating, wherein the first coating at least partially covers the first portion. The cutting tool also includes a second portion between the shank and the first portion, wherein the second portion includes the second coating, and wherein the second coating at least partially covers the second portion.

A hard film-coated cutting tool comprises: a hard base material and a hard film formed on the hard base material, wherein: assuming that a colorimetric diffusion reflectance value is L.sub.SCER and a total reflectance value is L.sub.SCIR, the relationship of 0.65L.sub.SCER/L.sub.SCIR0.85 is satisfied, and when surface roughness is measured on the rake surface of the hard film within the range of 100 m from the edge, an arithmetic average height S.sub.aR is within the range of 0.2 mS.sub.aR0.5 m; and assuming that, at a flank surface of the hard film, a colorimetric diffusion reflectance value is L.sub.SCEF and a total reflectance value is L.sub.SCIF, the relationship of L.sub.SCEF/L.sub.SCIF0.9 is satisfied, and when surface roughness is measured on the flank surface of the hard film within the range of 100 m from the edge, an arithmetic average height S.sub.aF is within the range of 0.15 mS.sub.aF0.4 m.

A coated cutting tool has a base material of a WC-based cemented carbide and a film formed on the surface of the base material by a chemical vapor deposition method. The coated cutting tool has a rake face, a flank face and a cutting edge ridgeline part positioned between the rake face and the flank face being provided, wherein a total film thickness of the entire film is 3 to 20 m in an average film thickness, and one or more oblique cracks where an extension angle of the crack to the surface of the film is 45 or less are present at the rake face within 300 m from the cutting edge ridgeline part.