A straight line along the second line segment and a straight line along the fourth line segment form an acute angle. The straight line along the second line segment and the straight line along the third line segment form an obtuse angle. The straight line along the first line segment and the straight line along the fourth line segment form an obtuse angle. Each of the third curved portion and the fourth curved portion is larger in radius of curvature than the first curved portion and larger in radius of curvature than the second curved portion. In a direction perpendicular to the bottom surface, a distance between the top surface and the bottom surface is equal to a distance between the cutting edge and the bottom surface, or is shorter than the distance between the cutting edge and the bottom surface.

The disclosure relates to a method of manufacturing a cutting tool including the steps of: providing a cutting tool blank including a cutting edge, defined by a cross-sectional wedge angle (β). The wedge angle has a variation along the cutting edge, and material is removed from the cutting edge with a constant material removal rate per length unit of the edge, such as to form a corresponding variation of edge rounding along the cutting edge. The disclosure further relates to a cutting tool including the cutting edge defined by the cross-sectional wedge angle having a variation along the cutting edge and wherein the cutting edge has a corresponding variation of edge rounding along the cutting edge.

A lubricant material for assisting machining process comprising fullerene.

In this drill, a cutting edge, which is formed at an intersecting ridge line part between a wall surface, facing a drill rotation direction, of a chip discharging flute formed at an outer periphery of a tip portion of a drill main body that is rotated around an axis, and a tip flank face, includes an inner peripheral cutting edge located on a radially inner peripheral side with respect to the axis; and an outer peripheral cutting edge connected to a radially outer peripheral side of the inner peripheral cutting edge. A point angle of a portion of the inner peripheral cutting edge on an inner peripheral side with respect to the axis is within a range of 90° to 170°.

A lubricant material for assisting machining process comprising fullerene.

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.

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.

Provided are a hole formation method enabling the formation of a high-quality hole even when a workpiece material is a difficult-to-machining metal material or a fiber-reinforced composite material and a drill bit used in the method. A drill bit includes at least one cutting edge and a leading flank adjacent to the cutting edge, and the leading flank is set to have a surface roughness Ra of 2.0 m or more and 3.0 m or less. A hole formation method includes a hole formation step of machining a portion to be processed of a workpiece material by means of drilling to form a hole while a lubricant material for assisting machining process is in contact with a drill bit and/or the portion to be processed, and in the hole formation step, the drill bit is used.

A cutting tool for cutting a hole into a fluid transportation pipe and for retaining a cutting chip is provided. The tool (1) comprises a main body (2) having an end which is prolonged by a tapered part (3), the tool (1) further comprising an accommodation space (11), the tool being configured to receive a cutting chip in the accommodation space (11) via an opening (10) which extends at least from a geometrical apex (5) of the tapered part (3) to the periphery of the main body (61), and the tool (1) further has a cutting edge (4) extending at least from the geometrical apex (5) of the tapered part (3) to the periphery of the main body (2) of the cutting tool (1). The main body (2) is made of a material that differs from a material of which the cutting edge (4) is made.

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.