That random moment I found out old Leicas use a different thread pitch than I thought

I was digging through a parts bin I picked up at an estate sale in Dayton last month, and I found a lens mount that looked exactly like a standard M39. But when I tried to screw it onto a body, it jammed up halfway. Looked it up online and turns out some older screw-mount Leicas use a thread pitch of 26 threads per inch instead of the standard 24. Who knew? I felt like an idiot for forcing it a little before I caught myself. Has anyone else run into weird thread mismatches on vintage stuff?

2 comments

2 Comments

umar592d agoTop Commenter

The Dayton area has some great estate sales for camera stuff, I've found a few weird pieces there myself. @raymitchell is right about Whitworth threads being a pain, I messed up a Compur shutter once that had them and it was a nightmare to fix. That 26 TPI on those old Leicas is a real trap, especially since the mounts look identical until you try to force them. I bet a lot of people have damaged their gear that way without realizing it until it's too late.

raymitchell2d ago

Yeah it's wild how fine the differences are on old gear. I messed up an adapter once because I didn't realize the threads were Whitworth vs metric, same kind of jam.