Screw tap and method for the production of a screw tap

A method for the production of screw taps, which are rotatable about a rotational axis, comprising:

• a) producing, for each screw tap, an associated number of thread-cutting teeth, wherein each of the thread-cutting teeth respectively has a radially outer tip cutter and are disposed mutually offset, with a predefined thread pitch, in an arrangement running spirally or helically around the rotational axis;
• b) wherein, in a lead region adjoining one end of the screw tap axially to the rotational axis, the maximum radial distance of the tip cutters of the thread-cutting teeth from the rotational axis increases with increasing axial distance of the tip cutters from one end of the screw tap, according to a predefined radial distance function,
• c) wherein radial is defined as perpendicular to the rotational axis and axial is defined as along or parallel to the rotational axis,
• d) wherein at least some of the thread-cutting teeth in the lead region respectively have a defined cutter rounding between tool face and tool flank comprising an outer surface that is separated from an ideal wedge shape by a reduction depth, wherein the ideal wedge shape is an unrounded cutting edge defined by an end point of intersecting lines extending from tool face and tool flank, and wherein the curvatures of the cutting edge roundings and the reduction depths are respectively chosen based on:
• d1) the number of thread-cutting teeth in the lead region;
• d2) the thread pitch;
• and
• d3) the increase in the maximum radial distance of the tip cutters of the thread-cutting teeth in the lead region, or the radial distance function of the thread-cutting teeth in the lead region of the respective screw tap.

A set of screw taps, comprising:

• two or more screw taps, each of which is rotatable about a rotational axis, and is configured with one or more rounded teeth, wherein the rounding of each tooth is configured to minimize wear and to otherwise maximize the life of the screw tap, each of the screw taps comprising:
• a plurality of thread-cutting teeth, which respectively have a radially outer tip cutter and are disposed mutually offset, with a predefined thread pitch, in an arrangement running spirally or helically around the rotational axis;
• wherein, in a lead region adjoining one end of the screw tap axially to the rotational axis, the maximum radial distance of the tip cutters of the thread-cutting teeth from the rotational axis increases with increasing axial distance of the tip cutters from a free end or tip of the screw tap;
• wherein at least some of the thread-cutting teeth in the lead region are curved relative to an ideal wedge shape having an outer edge defined as an end point of intersecting lines extending from tool face and tool flank, such that a distance from the intersection to the outer edge comprises a reduction depth, and wherein the reduction depth and curvature of the outer edge depend on:
• 1) the number of thread-cutting teeth in the lead region;
• and
• 2) the thread pitch;
• wherein the reduction depths of the cutter roundings of at least some of the thread-cutting teeth in the lead region are directly proportional to the thread pitch and inversely proportional to the number of thread-cutting teeth in the lead region,
• wherein the curvatures of the cutter roundings and reduction depths of the cutter roundings are chosen, in comparison to the ideal wedge shape, respectively based on the increase in the maximum radial distance of the tip cutters of the thread-cutting teeth in the lead region.