BOLT HOLE WITH IMPROVED THREADS AND TAP FOR MANUFACTURE THEREOF

摘要

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.

主权项

1. A bolt hole, comprising:
a part having a surface with said bolt hole extending into the part from the surface; threads in the hole having crests with a fishmouth shape at the crests defined by a central concave portion and raised corner portions at ends of the concave portion; and at least one start thread preceding the threads with the fishmouth shaped crests which has a substantially flat crest without the fishmouth shape.