Unusual (?) photographic screw thread?!?!?!

xkaes · Mar 3, 2023

At least to me it is.

I have TWO adapters/flanges that have the same screw thread size -- a size I've never run across.

The adapters are not related in any way -- other than that they are in my possession, and I'm trying to figure out what they are.

One is marked "for Nikon Japan", the other is unmarked.

One has a female screw thread that is the same size as the male screw thread on the other -- so they fit together fine, although, as I said, they are completely unrelated.

I have plenty of gear that has 40mm, 40.5mm and 42mm screw threads, but these two threads are between 40.5mm and 42mm.

What thread do you think it came be? I've never run across a 41mm or 41.5mm thread.

Just the puzzle of the day. And for anyone that wants to ask, "What are these adapters for?" or "What do these adapters do?" -- that's what I'm trying to figure out!

250swb · Mar 4, 2023

Nikon made some S series rangefinder lenses with the 40.5 diameter filter size (the 50mm f/2 and f/1.5 for example) but the pitch of the thread was different to Leica etc.. Are you sure it's not a 40.5 adapter but with the odd Nikon thread pitch?

xkaes · Mar 4, 2023

If it were the same diameter, but a different pitch size, it would start to connect. These won't.

For example, you can connect a Pentax M42 device (42x1.0mm) to a T-mount device (42x0.75mm) for at least one turn -- until it binds.

These are larger than 40.5mm and smaller than 42mm. I am assuming that they are 41mm. It's just that I have never heard if 41mm devices.

Dustin McAmera · Mar 4, 2023

There's a list of lens-mounts by William-Jan Markerink, re-published by Stephen Westin at Cornell Uni:

Alphabetical List of Camera Mounts

That gives the Wrayflex mount as M41.2x26tpi. Might that be what you have?

xkaes · Mar 4, 2023

Thanks, but for some reason I doubt that anyone would have made a Wrayflex lens adapter / flange marked "for Nikon".

That is an interesting list -- even though it lacks more information than it has.

Dustin McAmera · Mar 4, 2023

The Wrayflex series overlaps comfortably in date with Nikon rangefinders. I was thinking that if I had a camera as obscure as the Wrayflex, with a choice of six or eight native lenses, I might be glad of a mount adapter. But those Nikon RFs do have a recognisable mount (like but not like a Contax), and the back-focus would probably be all wrong.

You could describe what you have more fully. We know that you have one adapter with a male thread in the interesting size, and another with the same thread but female. What is on the other end of each? How long are they? What finish do they have? How old do they look?

OAPOli · Mar 4, 2023

Can you measure it with calipers? Without a thread gauge you can estimate the thread pitch as OD (male) minus ID (female).

xkaes · Mar 4, 2023

Both adapters simply have backs to be attached with pins/screws. I'll take a picture. These are unusual.

xkaes · Mar 4, 2023

Here are the mystery adapters. The one marked "NIKON" has a 4?.?mm female thread, and the other a matching 4?.?mm male thread.

The other photo shows what the opposite side looks like --from the side. It is designed to attach to something that has three pins/screws -- much like a T-2 adapter -- that push up into the groove and grab it.

OAPOli · Mar 4, 2023

FWIW, T-mount adapters have the exact same markings

xkaes · Mar 4, 2023

I have no idea what "exact same marking" you are referring to, but the threads on these two adapters are smaller than 42mm -- which is what T-mount have.

And the threads are bigger than 40.5mm.

I think I've figured out the problem. The 42mm adapter that I was using to test these two mystery items is defective. To my eye the threads look fine, but it must be warped, and won't fit.

So I got another 42mm item which fits fine.

Sorry for the trouble!!!

AnselMortensen · Mar 4, 2023

OAPOli said:
FWIW, T-mount adapters have the exact same markings

My guess is that the "for Nikon" piece is part of an adapter that connects a macro bellows/slide duper to a Nikon via a T-mount.
Some T-mounts are 2-piece, and have set screws that ride in a v-shaped groove so that camera/lens/slide stage all align properly.
I believe your "for Nikon" ring is one piece of a 2-piece T-mount.

Unusual (?) photographic screw thread?!?!?!

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