A surface-coated cutting tool includes a substrate and a coating formed on a surface of the substrate, the coating including one or two or more layers, at least one of the layers being an Al-rich layer including hard particles, the hard particle having a sodium chloride type crystal structure, and including a first unit phase in a form of a plurality of lumps and a second unit phase interposed between the lumps of the first unit phase, the first unit phase being composed of a nitride or carbonitride of Al.sub.xTi.sub.1-x, the first unit phase having an atomic ratio x of Al of 0.7 or more and 0.96 or less, the second unit phase being composed of a nitride or carbonitride of Al.sub.yTi.sub.1-y, the second unit phase having an atomic ratio y of Al exceeding 0.5 and less than 0.7.

A surface-coated cutting tool includes a substrate and a coating formed on a surface of the substrate, the coating including one or two or more layers, at least one of the layers being an Al-rich layer including hard particles, the hard particle having a sodium chloride type crystal structure, and including a first unit phase in a form of a plurality of lumps and a second unit phase interposed between the lumps of the first unit phase, the first unit phase being composed of a nitride or carbonitride of Al.sub.xTi.sub.1x, the first unit phase having an atomic ratio x of Al of 0.7 or more and 0.96 or less, the second unit phase being composed of a nitride or carbonitride of Al.sub.yTi.sub.1y, the second unit phase having an atomic ratio y of Al exceeding 0.5 and less than 0.7.

A surface-coated cutting tool includes a substrate and a coating formed on a surface of the substrate, the coating including one or two or more layers, at least one of the layers being an Al-rich layer including hard particles, the hard particle having a sodium chloride type crystal structure, and including a first unit phase in a form of a plurality of lumps and a second unit phase interposed between the lumps of the first unit phase, the first unit phase being composed of a nitride or carbonitride of Al.sub.xTi.sub.1-x, the first unit phase having an atomic ratio x of Al of 0.7 or more and 0.96 or less, the second unit phase being composed of a nitride or carbonitride of Al.sub.yTi.sub.1-y, the second unit phase having an atomic ratio y of Al exceeding 0.5 and less than 0.7.

A surface-coated cutting tool including a substrate including a rake face and a flank face and a coating which covers a surface of the substrate is provided. The substrate is made of a cBN sintered material or a ceramic sintered material. The coating includes an alternating layer. The alternating layer is made by alternately stacking a first layer and a second layer different in composition from the first layer. The first layer contains Al, Cr, and N. The second layer contains Ti, Al, and N. A ratio T1/T2 between a thickness Ti of the first layer and a thickness T2 of the second layer is not lower than 0.1 and lower than 1. There are thirty or more interfaces at which the first layer and the second layer are in contact with each other.

A hard coating includes two first crystalline phases, and a second crystalline phase disposed between the two first crystalline phases. The two first crystalline phases each include, independently, a laminate structure having a Ti.sub.1-x1Al.sub.x1N phase having a sodium chloride-type crystal structure, and an Al.sub.x2Ti.sub.1-x2N phase having a sodium chloride-type crystal structure that are alternately stacked. An Al composition ratio x1 of the Ti.sub.1-x1Al.sub.x1N phase satisfies a relationship 0.5x10.75, and an Al composition ratio x2 of the Al.sub.x2Ti.sub.1-x2N phase satisfies a relationship 0.75<x20.95. The laminate structure includes a region in which an Al concentration periodically changes along a stacking direction of the Ti.sub.1-x1Al.sub.x1N phase and the Al.sub.x2Ti.sub.1-x2N phase. In this region, a difference between a maximum value of the Al composition ratio x2 and a minimum value of the Al composition ratio x1 is greater than 0.25. The second crystalline phase contains AlN having a wurtzite-type crystal structure.

The invention provides a tool, a method and a machine with which roof ridge-shaped chamfers can be produced on teeth of an internally and externally toothed gearwheel with minimised changeover times during tool set up. For this purpose, a tool according to the invention comprises a tool carrier having a holding section for attachment in a tool holder and a chamfering tool, which is held on the end section of the tool carrier, said end section being associated with the other end face, and during use describes an impact circle with its cutting edge, the diameter of said circle being determined by the radial distance of the cutting edge of the chamfering tool from the axis of rotation of the tool. According to the invention, at least one further chamfering tool is attached in a middle section of the tool carrier which is offset relative to the end section provided with the chamfering tool towards the holding section of the tool carrier. At the same time, the further chamfering tool is held with its cutting edge at a radial distance from the axis of rotation of the tool, which is greater than the radial distance of the cutting edge of the chamfering tool held on the end section of the tool holder. A method according to the invention and a machine according to the invention are based on the use of tools according to the invention.

A sintered material includes a first material and a second material, the first material being partially stabilized ZrO.sub.2 having a crystal grain boundary or crystal grain in which 5 to 90 volume % of Al.sub.2O.sub.3 is dispersed with respect to a whole of the first material, the second material including at least one of SiAlON, silicon nitride and titanium nitride, the sintered material including 1 to 50 volume % of the first material.

A sintered material includes a first material and a second material, the first material being partially stabilized ZrO.sub.2 having a crystal grain boundary or crystal grain in which 5 to 90 volume % of Al.sub.2O.sub.3 is dispersed with respect to a whole of the first material, the second material including at least one of SiAlON, silicon nitride and titanium nitride, the sintered material including 1 to 50 volume % of the first material.

A skiving cutter includes a cutting edge portion in which a tooth trace extends in a direction inclined with respect to an axis of a base. The cutting edge portion is segmented into a plurality of segmented cutting edges by cutting edge grooves extending in a direction intersecting the tooth trace. A helix angle is different according to positions of the plurality of segmented cutting edges.

A simulation apparatus includes: a memory to store information on the shape of a workpiece, information on a cross section of a portion of the workpiece, and information on definition points indicating the shape of an edge surface of tool edges of a machining tool; a first calculator to perform a calculation to obtain passage points in a three-dimensional coordinate system; a second calculator to cause the cross section in the three-dimensional coordinate system to be disposed parallel to a plane defined by predetermined two of the axes of the three-dimensional coordinate system, thus converting the passage points in the three-dimensional coordinate system into passage points in a two-dimensional coordinate system; and a third calculator to decide, in accordance with the passage points in the two-dimensional coordinate system, the shape of a tooth profile to be formed on the workpiece in the two-dimensional coordinate system.