DIYbanter - View Single Post - Tapping holes.....sloppy threads inevitable

wrote in news:1113431278.985045.226760
@f14g2000cwb.googlegroups.com:

Thanks guys for all your help. I still have some more questions.
First of all to answer Pete's question, the fit of the bolt is really
loose, especially the first 3 or 4 threads. If put to the test
they usually will strip out.

What material are you tapping? Are you hand tapping? And most important
have you checked your hole for size and taper? Also, how many threads are
engaged between the bolt and your part?

snip (already answered)
Finally, what do you guys think of a spiral pointed tap for open-ended
holes?

Depends on the answer to the above questions. If you have a drill press,
knee mill, lathe, etc. and can power tap, rather than hand tap, you may
want to consider a roll form tap. Formed threads are stronger than cut
threads. If you are tapping a soft material and are using hardened bolts,
then it wouldn't take too much torque to strip out the threads with a small
thread like a 1/4-20, particularly if you only have a few threads engaged.

--

Dan