A surface-coated cutting tool includes a base material and a coating film formed on a surface of the base material. The coating film includes a first alternating layer and a second alternating layer formed on the first alternating layer. The first alternating layer includes first and second layers. The second alternating layer includes third and fourth layers. One or a plurality of the first layers and one or a plurality of the second layers are layered alternately, and one or a plurality of the third layers and one or a plurality of the fourth layers are layered alternately.

A method for producing a threaded bore in a workpiece with a tapping tool bit, which, at its drill bit tip, has a main cutting lip and a thread profile trailing in a tapping direction (I) with at least one thread cutting tooth, wherein, in a tapping stroke (G), the main cutting lip produces a core hole and, at the same time, the thread profile forms an internal thread at the inner wall of the core hole until reaching an intended thread depth (t.sub.G), specifically with a tapping feed (f.sub.G) in the tapping direction (I).

A tap 1 has a threaded portion 2 including a cutting blade 5 on an outer circumferential surface, a flute portion 3 that divides the threaded portion 2 in a circumferential direction, and a shank portion 4 formed continuously from the threaded portion 2 and the flute portion 3 along a central axis O. The flute portion 3 includes, in a cross-sectional view, a first flute 31 formed continuously from the cutting blade 5 of the threaded portion 2, a second flute 32 formed continuously from the first flute 31, and a ridge line portion 33 being a boundary between the first and second flutes 31, 32. A distance e from the central axis O to the ridge line portion 33 is longer than a distance d1 and a distance d2, respectively.

A tap 1 has a threaded portion 2 including a cutting blade 5 on an outer circumferential surface, a flute portion 3 that divides the threaded portion 2 in a circumferential direction, and a shank portion 4 formed continuously from the threaded portion 2 and the flute portion 3 along a central axis O. The flute portion 3 includes, in a cross-sectional view, a first flute 31 formed continuously from the cutting blade 5 of the threaded portion 2, a second flute 32 formed continuously from the first flute 31, and a ridge line portion 33 being a boundary between the first and second flutes 31, 32. A distance e from the central axis O to the ridge line portion 33 is longer than a distance d1 and a distance d2, respectively.

A method for producing a threaded hole in a workpiece with a thread tapping tool bit, which, at its drill bit tip, has a main cutting edge and a thread profile that trails in a thread tapping direction with at least one thread cutting tooth, wherein, in a thread tapping stroke, the main cutting edge produces a core hole, and, at the same time, the thread profile forms an internal thread at the inner wall of the core hole until a target thread depth is reached, and this is conducted with a thread tapping advance in the thread tapping direction and at a thread tapping rotational speed of the thread tapping tool bit synchronized therewith. After the thread tapping stroke, an oppositely directed reversing stroke is produced, in which the thread tapping tool bit is withdrawn out from the threaded hole in a reversing direction and, in fact, this is conducted with an opposite reversing feed.

A method for producing a threaded hole in a workpiece with a thread tapping tool bit, which, at its drill bit tip, has a main cutting edge and a thread profile that trails in a thread tapping direction with at least one thread cutting tooth, wherein, in a thread tapping stroke, the main cutting edge produces a core hole, and, at the same time, the thread profile forms an internal thread at the inner wall of the core hole until a target thread depth is reached, and this is conducted with a thread tapping advance in the thread tapping direction and at a thread tapping rotational speed of the thread tapping tool bit synchronized therewith. After the thread tapping stroke, an oppositely directed reversing stroke is produced, in which the thread tapping tool bit is withdrawn out from the threaded hole in a reversing direction and, in fact, this is conducted with an opposite reversing feed.

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.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.