A thread-cutting tap includes: a thread portion having an external thread, and including a chamfered portion and a complete thread portion that is axially adjacent to the chamfered portion; a flute extending from an axially distal end of the tap toward an axially proximal end of the tap; a rake face defined by one of widthwise opposite end portions of the flute; and a cutting edge defined by one of widthwise opposite edges of the flute, so as to be adjacent to the rake face and extend along the flute. The cutting edge is provided with a protrusion portion at least in a radially outer end portion of the chamfered portion, such that the protrusion portion protrudes from the rake face forwardly in the rotation direction and extends along the cutting edge.

A spiral flute tap includes a body having an axial forward end and an axial rearward end. The body has a cylindrical shank portion adjacent the axial rearward end, a threaded fluted portion adjacent the axial forward end, a non-threaded fluted portion between the cylindrical shank portion and the threaded fluted portion, and a central, longitudinal axis. The spiral flute tap further includes a plurality of helical flutes formed at a helix angle, HA, with respect to the central, longitudinal axis of the tap that continuously increases in magnitude in the threaded fluted portion. In other words, the lead of the plurality of helical flutes continuously decreases in magnitude in a rearward direction for a predetermined distance. In one example, the helix angle, HA, varies at a rate of between 0.5 degrees/mm to 4.0 degrees/mm. A method of making the spiral flute tap is also disclosed.

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 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 method for producing a tapped bore in a workpiece with a tap drill bit, which, at its drill bit tip, has a primary cutting edge and a thread profile trailing in a tap drilling direction. The method has a tap drilling stroke, in which the tap drill bit is driven into the workpiece with a tap drilling advance in the tap drilling direction and at a tap drilling rotational speed synchronized therewith, and the tool-primary cutting edge produces a core-hole bore, and the thread profile of the tool bit forms an inner thread at the inner wall of the core-hole bore. In the tap drilling stroke, shavings are produced, which are conveyed in a shavings discharge direction, which is oppositely directed to the tap drilling direction, out from the tapped bore and collide here with thread flanks of the inner thread that face the shavings that are discharged.

A method for producing a tapped bore in a workpiece with a tap drill bit, which, at its drill bit tip, has a primary cutting edge and a thread profile trailing in a tap drilling direction. The method has a tap drilling stroke, in which the tap drill bit is driven into the workpiece with a tap drilling advance in the tap drilling direction and at a tap drilling rotational speed synchronized therewith, and the tool-primary cutting edge produces a core-hole bore, and the thread profile of the tool bit forms an inner thread at the inner wall of the core-hole bore. In the tap drilling stroke, shavings are produced, which are conveyed in a shavings discharge direction, which is oppositely directed to the tap drilling direction, out from the tapped bore and collide here with thread flanks of the inner thread that face the shavings that are discharged.

A spiral flute tap includes a body having an axial forward end and an axial rearward end. The body has a cylindrical shank portion adjacent the axial rearward end, a threaded fluted portion adjacent the axial forward end, a non-threaded fluted portion between the cylindrical shank portion and the threaded fluted portion, and a central, longitudinal axis. The spiral flute tap further includes a plurality of helical flutes formed at a helix angle, HA, with respect to the central, longitudinal axis of the tap that continuously increases in magnitude in the threaded fluted portion. In other words, the lead of the plurality of helical flutes continuously decreases in magnitude in a rearward direction for a predetermined distance. In one example, the helix angle, HA, varies at a rate of between 0.5 degrees/mm to 4.0 degrees/mm. A method of making the spiral flute tap is also disclosed.

In one aspect, thread forming taps are described herein. In some embodiments a thread forming tap comprises a shank disposed at a first end adapted to engage a tool holder and an elongated working portion disposed at a second end. The working portion comprises at least one helical thread and a plurality of longitudinally-extending linear grooves. The longitudinally-extending linear grooves intersect the helical thread forming a plurality of lobes, wherein adjacent lobes differ from one another in relief type and/or relief rate.

The invention relates to methods for producing a thread with a predetermined thread pitch in a workpiece.

A method for producing a thread can include a) generating a number n1 of twisted grooves in a wall of the workpiece encircling a thread axis (M) or generating a wall of the workpiece which has a number n1 of twisted grooves and encircles a thread axis, b) respectively inserting a thread generating region of a tool into each of the twisted grooves in a twisted insertion movement, c) generating a thread in each wall sub-region, adjoining the groove(s), of the wall of the workpiece by rotating the tool about the thread axis (M) and with a simultaneous axial feed motion of the tool coaxially with respect to the thread axis with a particular axial feed speed and d) moving each thread generating region of the tool out of the associated groove in a twisted removal movement matched to the twisting of the associated twisted groove.