In a screw thread cutter, a screw thread-cutting edge is formed on an outer periphery of a tip portion of a cutter body. Finishing edge-thread ridge height from a tangent line passing through valley bottoms of second and third valley portions to outer peripheral ends of first and second finishing edges are equal to each other. A preceding edge-thread ridge height from the tangent line to an outer peripheral end of a preceding edge is lower than each of the finishing edge-thread ridge height. A first valley portion-depth from the outer peripheral end of the first finishing edge to the valley bottom of the first valley portion is deeper than a second valley portion-depth from the outer peripheral end of the second finishing edge to the valley bottom of the second valley portion.

The invention relates to a thread milling cutter for manufacturing an internal thread, wherein the thread milling cutter has at least one section with multiple teeth, wherein a pitch is arranged between every two adjacent teeth, wherein the predominant number of pitches corresponds to a desired pitch and there is at least one pitch that deviates from the desired pitch.

The invention further relates to a method for manufacturing an external thread on a component or an internal thread in a component, wherein, in one step, a thread milling cutter according to the invention is advanced into the wall of the component and in another step, the thread milling cutter is moved along the extent of the wall once and in this way is moved in the axial direction by one lead of a thread turn.

In a screw thread cutter, a screw thread-cutting edge is formed on an outer periphery of a tip portion of a cutter body. Finishing edge-thread ridge height from a tangent line passing through valley bottoms of second and third valley portions to outer peripheral ends of first and second finishing edges are equal to each other. A preceding edge-thread ridge height from the tangent line to an outer peripheral end of a preceding edge is lower than each of the finishing edge-thread ridge height. A first valley portion-depth from the outer peripheral end of the first finishing edge to the valley bottom of the first valley portion is deeper than a second valley portion-depth from the outer peripheral end of the second finishing edge to the valley bottom of the second valley portion.

In a part having a surface, a bolt hole is provided extending into the part from the surface. Threads in the hole have crests with a fishmouth shape at the crests defined by a central concave portion and raised corner portions at ends of the concave portion. At least one start thread preceding the threads with the fishmouth shape crests is provided having a substantially flat crest without the fishmouth shape. A tap for manufacturing the threaded bolt hole has a first thread section and a second thread section. The second thread section has a plurality of threads for creating at least one improved start thread in the hole to be threaded, minor diameters at valleys between the threads of the second thread section being greater than minor diameters at valleys between threads of the first thread section or major diameters at crests of the threads of the second thread section being greater than major diameters at crests of the first thread section.