A cutting tool according to the present disclosure has a rake face, a flank face, and a cutting edge. The cutting edge is located between the rake face and the flank face. The cutting tool includes a substrate composed of a cubic boron nitride sintered material, and an oxide layer that covers the substrate and that constitutes at least part or whole of the rake face, the flank face, and the cutting edge. The oxide layer includes at least one element selected from a group consisting of titanium, aluminum, zirconium, and cobalt. A thickness of the oxide layer is 2 μm 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 allow so-called freedom of feed during cutting to be improved. A cutting edge body of a cutting insert includes a front cutting edge formed on one end side in a longitudinal direction, the front cutting edge being a cutting edge formed on an intersecting edge between a peripheral side surface and an upper surface of the cutting edge body having a prismatic shape, a side cutting edge formed on one end side in a lateral direction, a recessed part provided in the upper surface of the cutting edge body to be subsequent to the side cutting edge in the lateral direction, and a wall part having a wavy wall surface formed in a portion of the recessed part and a discrete wall surface formed at a position between the wavy wall surface and the side cutting edge and including a plurality of surfaces which are discrete along the longitudinal direction.

A method of manufacturing a drill bit includes providing a piece of bar stock having a first end, a second end opposite the first end, and an axis of rotation extending centrally through the bar stock between the first and second ends, cutting the first end of the bar stock to form a first tip angle at an oblique angle measured through the axis of rotation, cutting the first end of the bar stock at a second tip angle measured through the axis of rotation to form first tip surfaces and second tip surfaces. The first tip surfaces have the first tip angle and the second tip surfaces have the second tip angle. The second tip angle is smaller than the first tip angle. Finally forming a flute in the bar stock between the first and second ends and forming a shank at the second end of the bar stock.

A drill bit includes a body having a first end, a second end opposite the first end, and an axis of rotation extending centrally through the body. The drill bit includes a cutting head with a cutting tip on the axis of rotation and a cutting portion. The cutting portion includes first tip surfaces on opposite sides of the axis of rotation and second tip surfaces on opposite sides of the axis of rotation. Each first tip surface extends radially outward from the cutting tip to a corresponding second tip surface. Each second tip surface extends from a corresponding first tip surface to an outer periphery of the body. The first tip surfaces define a first tip angle measured through the axis of rotation that is oblique. The second tip surfaces define a second tip angle measured through the axis of rotation that is smaller than the first tip angle.

A cutting tool, comprising a substrate having a cutting surface and a coating adhered to the cutting surface in a solid state, wherein the coating includes a soft metal and is capable of melting and functioning as an in-situ liquid lubricant when the cutting tool is applied in a machining operation. Also, a method of applying a coating to a cutting tool, comprising receiving a premachining workpiece, the premachining workpiece formed of a coating material including a soft metal; and machining the premachining workpiece with the cutting tool such that a layer of the coating material adheres to a cutting surface of the cutting tool in a solid state.

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.

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 allow so-called freedom of feed during cutting to be improved. A cutting edge body of a cutting insert includes a front cutting edge formed on one end side in a longitudinal direction, the front cutting edge being a cutting edge formed on an intersecting edge between a peripheral side surface and an upper surface of the cutting edge body having a prismatic shape, a side cutting edge formed on one end side in a lateral direction, a recessed part provided in the upper surface of the cutting edge body to be subsequent to the side cutting edge in the lateral direction, and a wall part having a wavy wall surface formed in a portion of the recessed part and a discrete wall surface formed at a position between the wavy wall surface and the side cutting edge and including a plurality of surfaces which are discrete along the longitudinal direction.

A surface coated cutting tool comprises a base material and a coating layer that coats the base material, the coating layer including an alternate layer composed of a first unit layer and a second unit layer alternately stacked, the first unit layer being composed of a nitride containing aluminum and zirconium, in the first unit layer, when the total number of metal atoms constituting the first unit layer is represented as 1, a ratio thereto of the number of atoms of the zirconium being not less than 0.65 and not more than 0.95, the second unit layer being composed of a nitride containing titanium and aluminum, in the second unit layer, when the total number of metal atoms constituting the second unit layer is represented as 1, a ratio thereto of the number of atoms of the aluminum being larger than 0.40 and not more than 0.70.

A small-diameter drill in which is a double margin having a diameter of 2 mm or less and a ratio of a margin length to a diameter of 3 or more, in which the margin length L in an axial direction from an outer peripheral end of a cutting edge to the rear ends of first and second margin parts and a ratio L/D to a diameter D are 3 or more, in which at least a surface of a chip discharge groove is provided with a hard coating made of nitride, in which a surface of the hard coating in the chip discharge groove has skewness (Ssk) defined in ISO25178 of less than 0, and in which the number of droplets having an equivalent circle diameter of 1.0 μm or more is 5 or less per 100 μm.sup.2 in cross-section observation of the hard coating.

A hard film for coating a surface of a base material, the hard film includes a layer A, a layer B, and a nanolayer-alternating layer. The layer A is an AlTiCr nitride of (Al.sub.aTi.sub.bCr.sub.cα.sub.d)N, where α is one or more elements selected from C, B, Si, V, Y, Zr, Nb, Mo, Hf, Ta, and W. The layer B is an AlTiCr nitride or AlTiCr carbonitride of (Al.sub.eTi.sub.fCr.sub.gβ.sub.h)C.sub.xN.sub.1-X, where β is one or more elements selected from B, Si, V, Y, Zr, Nb, Mo, Hf, Ta, and W. The nanolayer-alternating layer is formed by alternately laminating a nanolayer A or a nanolayer B having the same composition as the layer A or B. And, the layer C is an AlCr(SiC) nitride or AlCr(SiC) carbonitride of [Al.sub.iCr.sub.j(SiC).sub.kγ.sub.l]C.sub.YN.sub.1-Y, where γ is one or more elements selected from B, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W.