Praktica's I have Won

[John Parry]

Hi Ron,

Regarding the Soligor 400/6.3 That's the same lens as I had the discussion with PeterW about - it stopped screwing in to my Prakticas. Peter thinks its because its a T-mount. If you find it binding, it may be the same problem.

Regards - John

[doubs43]

johnrparry said:

Hi Ron, Regarding the Soligor 400/6.3 That's the same lens as I had the discussion with PeterW about - it stopped screwing in to my Prakticas. Peter thinks its because its a T-mount. If you find it binding, it may be the same problem. Regards, John

John, would you please explain how an undamaged T-Mount creates a problem with mating to a Praktica? Unless the camera threads or the mount threads have been somehow damaged, I don't see how there could be a problem.

Walker

[PeterW]

Hope you don't mind my jumping in here, John.

It's not the T mount adaptor itself that gives the problem, Walker, its the thread on the end of a lens that takes a T mount. For some reason best known to the makers this is 42mm x 0.75mm pitch thread. The thread on Prakticas, Pentaxes and so on is 42mm x 1.0mm pitch. When both threads are new they sometimes appear to marry OK, but when one or other of them gets a little worn they bind. I've found this several times on T mount lenses that are missing the actual T mount adaptor.

Peter

[John Parry]

No problem Peter - still looking out for that T-mount adapter. Sellers are vague about what they are actually selling. These adapters are also used for telescopes and microscopes, where the male/female and T-mount/M42 parts can be reversed.

Walker - I agree its hard to believe until you see it. Have a look at topic "M42 Threads" in the Workbench section for the background to this subject and how it came up.

Regards - John

[heath]

I have a T-mount to Canon FD adaptor that I used to use with a Hanimex 500mm f8 felex lens to mount it to my old T70. Now I don't have that body I have no use for it. The lens came with a T-mount to M42 adaptor so I can still use it with my Praktica's, Zenits and my Fujica.

Heath

[kamera]

John,

I remember the mismatch conversation in the thread, but not that it was the Soligor 400/6.3!

The Hanimex and Soligor I will have coming was stated for Pentax Spotmatic...there was no mention at all of a need for a T-mount. I was planning on being able to use both of them on my Spotmatic, Mamiya or Pratika since it was M42.

Will see what is what when they arrive. Gonna be a little while yet as, due to the holiday, my payment took 5 days to reach there instead of the post office statement of 2-3 days.

Thanks for the tip on perhaps a problem.

Ron Head
Kalamazoo, MI

[doubs43]

peterw said:

Hope you don't mind my jumping in here, John. It's not the T mount adaptor itself that gives the problem, Walker, its the thread on the end of a lens that takes a T mount. For some reason best known to the makers this is 42mm x 0.75mm pitch thread. The thread on Prakticas, Pentaxes and so on is 42mm x 1.0mm pitch. When both threads are new they sometimes appear to marry OK, but when one or other of them gets a little worn they bind. I've found this several times on T mount lenses that are missing the actual T mount adaptor. Peter

Peter, thanks for the explaination and that makes perfect sense. I've never encountered this problem as I've always used an adapter and never tried screwing my T-Mount lenses directly onto the camera.

Like you, I find it odd that the manufacturer would use a thread pitch different than that on the camera. Perhaps they didn't anticipate mounting the lens directly without an adapter.

Walker

[Rachel]

I guess it was silly for the maufacturers to design the T-mount with the same mount diameter as the Praktica at 42mm as it was bound to cause confusion. Of course if a lens is a T-mount lens then it does need the adaptor if only to get the back register correct.

On the subject of thread pitches I have read that some manufacturers initially got the pitch wrong for M39 lenses which do do not have a metric pitch at all but is 24 turns/inch. I think, off my head, that is right but I'm sure that someone will correct me if I recall incorrectly

[PeterW]

Hi Rachel,

You're right, the Leica screw thread mount is not a metric thread even though it is 39mm diameter. It has 26 threads per inch, and is a Whitworth profile thread.

M39 metric thread is also 39mm diameter but has a pitch of 1mm, or 25.4 tpi and, naturally, a metric profile thread.

The Whitworth thread profile is a hangover from the early days of Leitz microscopes when Whitworth profile threads were used by most of the optical industry in Europe. All Leitz thread cutting tools in the 1920s were Whitworth profile, and this was maintained on Leica thread mounts right up to the end to keep compatibility.

This is why the Leica thread mount is usually referred to as LTM and not M39.

The only instance I'm aware of of a lens maker being mistaken was in the very early days of FED cameras in Russia where, naturally, they used an M39 metric thread. This didn't matter because they weren't looking for compatibility with a Leica thread mount. However, after quite a short time the Russians changed to a 39mm by 26 tpi Whitworth form thread.

Peter

[Rachel]

Hi Peter.

Thanks for the corrections. I'd forgotten that there are other 39mm mount cameras apart from the Leica and it's copies.