A quick small job.
Wanted to fit a lens onto an astronomical camera (
http://www.myastroshop.com.au/guides/gstar/gstar-ex4.htm) for a friend.
My first attempt relied upon the expert who knew all about these cameras (not myastroshop) who told us it was a metric thread and checking it out with my thread gauge it appeared to be a 0.8mm thread which I duly cut.
Hmm, must have cut a taper thread as the lens only screwed in half way before binding.
I dug out an sae gauge that I've never used and double checked the original thread, hmm, it looks like a 32tpi thread also fits.
So I bored a hole and cut the 32tpi thread. Success, it screwed in all the way.