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[JasonBModerator @jasonb]

Posted by Howard Lewis on 18/09/2019 11:28:24:

26 tpi 60 degree form does not match as exactly as the 1 mm.pitch gauge.

Did you miss the bit about it also being Whitworth form not 60deg?

I wonder how much chance there is of a few turns of thread binding if 26tpi and 1mm pitch are mixed up, even less so when 55 & 60 deg angles are thrown into the mix.

[Howard LewisParticipant @howardlewis46836]

No Jason,

Didn't miss that bit either..

I checked Whit form thread as well.

Would it not be strange that makers of lenses, extension tubes and bellows would have got it wrong over the years, and made 1 mm pitch threads instead of 26 tpi whit form; (which would have been an alien thread to continental manufacturers of cameras and enlargers ) ?

The only Whit form threads that were popular in pre war years, and for some makers of tripods, post WW2 was 3/8 BSW, instead of the otherwise universal 1/4 BSW for attaching cameras.

Howard

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Howard Lewis on 18/09/2019 12:49:52:

[ …]

Would it not be strange that makers of lenses, extension tubes and bellows would have got it wrong over the years, and made 1 mm pitch threads instead of 26 tpi whit form; (which would have been an alien thread to continental manufacturers of cameras and enlargers ) ?

The only Whit form threads that were popular in pre war years, and for some makers of tripods, post WW2 was 3/8 BSW, instead of the otherwise universal 1/4 BSW for attaching cameras.

.

With some trepidation … I will try once more:

No one has suggested that the later incarnations [by various makers] of the 39mm screw thread were not 1mm pitch.

The fact remains, however, that the first screw-threaded Leicas were 39mm by 26tpi Whitworth form.

If you think about it; it is not at all improbable … Leitz was an established manufacturer of Microscopes, habitually using Royal Microscopical Society threads on its objectives, and therefore tooled-up for screw-cutting Imperial threads. Why would they not start-off by using 26tpi for the Leica ?

Please don't bother responding … I just ask that you research the matter thoroughly

… You obviously will not be persuaded by any reference which is not of your choosing.

MichaelG.

[peak4Participant @peak4]

Posted by Michael Gilligan on 18/09/2019 12:02:58:

I'm with you hereon in, since the various patents I've found don't specify the thread dimensions .
Much discussion on the Leica forum; to read it one needs to be a member, but I'll just leave this one link here.

FED/Zorki etc. were certainly 1mm pitch in their copies.

Bill

Edited By peak4 on 18/09/2019 18:14:31

[Howard LewisParticipant @howardlewis46836]

Quite right Michael!

Microscope threads would have been Imperial, Whit form.

A lot of Photographic Enlarging lenses used Whit form threads, (my beloved Taylor, Taylor Hobson Ental lenses do )

A lot of Continental and Japanese, lenses, such as Schneider, El Nikkor etc use the 39 x 1 mm thread (Mine do!)

But this argument is about Cameras. All my photographic books, and experience, stretching back over nearly 60 years, and manufacturers quote 39 x 1 mm. The Corfield Periflex, the Rusian Rangefinders (as well as the unusual Zenit 35M ) and the Japanese Leica copies, such as Tower and Canon, and accessory and lens manufacturers all quoted and used 39 x 1mm. It is only recently that the erroneous belief in 26 tpi has arisen.

Lets just agree to disagree!

Howard

[old martParticipant @oldmart]

To possibly clear up the argument about camera lens mount threads, have a look at the SRB Photographic web site, they manufacture pretty much every adaptor there is:

**LINK**

[JasonBModerator @jasonb]

They do only seem to list M39 not L39 which seems to be the Leica 26tpi form, plenty of adaptors with 26tpi at 39mm dia so have to assume there was a camera they fitted

Here, here, here etc

[BazyleParticipant @bazyle]

I have in my hand a 39mm tap. It is really difficult to decide whether it is 26tpi or 1mm with my plastic callipers but it is labelled 1mm. As it came from an engineer living near Kodaks in Harrow that explains why he had this unusual item. As it is still in wax unused perhaps it was purchased but was the wrong version for their equipment or they were intending to convert some of their imperial equipment just as it all went digital and the plant closed.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bazyle on 27/09/2019 13:42:53:

I have in my hand a 39mm tap. It is really difficult to decide whether it is 26tpi or 1mm with my plastic callipers but it is labelled 1mm. As it came from an engineer living near Kodaks in Harrow that explains why he had this unusual item. As it is still in wax unused perhaps it was purchased but was the wrong version for their equipment or they were intending to convert some of their imperial equipment just as it all went digital and the plant closed.

.

@ Bazyle, and old mart

The existence, and common usage, of M39x1mm is not in question …

If I recall correctly, the ‘error’ was first made by Canon and has persisted.

The matter under debate is simply what thread Leitz used when the screw-mount Leica was launched. … and as an interesting rider to that; whether Leitz ever succumbed.

MichaelG.

[peak4Participant @peak4]

Posted by Michael Gilligan on 27/09/2019 20:17:29:

If I recall correctly, the ‘error’ was first made by Canon and has persisted.

The matter under debate is simply what thread Leitz used when the screw-mount Leica was launched. … and as an interesting rider to that; whether Leitz ever succumbed.

MichaelG.

Everything I've read thus far, and it's quite extensive since the weather's been lousy, points to Barnack's use of a 39mm 26TPI thread on the Leica II through to the IIIc, and most sources point to it being chosen as Leitz were geared up to that pitch for microscope lenses.

Whilst there are claims it was patented, I've failed to find the original Reichspatentamt which ran from from 1931 to 1940. Since the LTM 39mm lenses were released in 1931, it was about the changeover period from the previous patent office. Post war of course, all German patents were voided as part of the war reparations, hence Leica patenting the M bayonet mount.

I've also tried several other worldwide patent searches, and found several by Leitz/Barnack, but not the relevant one specifying the pitch.

Schneider used to produce lenses, both for Leitz and in their own right; Google searches quote text from their web site referring to 39mm x 26TPI; see first link.

Unfortunately, Schneider have re-vamped the web site since this Google indexing, so the text is now missing. I've even tried using Wayback machine on their old site(s), but there isn't a snapshot at the relevant time. I think I narrowed it down to FAQ-10, but can't find it anywhere.

I'm not trying to force a point against anyone here, but pursuing it for my own interest now.

Bill

p.s. Leitz also made various lens adaptors to enable the use of LTM lenses on M mount, such as IRZ00 Part No. 14097, but I've failed to find the spec thus far.

Edited By peak4 on 27/09/2019 23:15:35

[HOWARDTParticipant @howardt]

Never owned a Leica, thread from reason new to me. Camera threads

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