This is a really good article about the different thread sizes and other info.
Hopefully it helps.
One thread problem I've ran into was from SvBONY. They said (and still say) their helical focuser is M36x1.0 threads when in fact they are M36.4x1.0 (as used by some Vixen/Takahashi products). And they will NOT admit that they are wrong.
I had an adapter made based on their info (i.e. M36x1.0) and of course it doesn't thread on. Fortunately the adapter maker knew that it must be M36.4 and sent me one made to those threads and it works great.
So good luck if you have to deal with them or another manufacturer who doesn't know their own products. Luckily another SvBONY product I have does have the correct threads; so not all of their stuff has wrong information.
Edited by lmclouth, 21 January 2021 - 06:21 AM.