One way to determine the pitch on a threaded hole is to force-screw a soft wood dowel of appropriate size into the hole. It will take the impression of the threads and then you can use a thread checker to try to determine the pitch. Once it is determined it may or may not yield a result that is easy to match. In replacing a stripped screw on a drilling's sidelock I once did this, but then had to drill and tap to another size, anyway.
That's a good idea. As far as match g whatever the thread is,inless it is somewhere between pitches, I can cut them on my lathe. I COULD drill/retap to the next nearest standard thread but dont think I would do that. I don't like making permanent modifications to historical things even though, being a restock, its already no longer "as made".
