Jupiter 8 Seating on Leica 111 Problem

[Baybers]

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I received my 1957 J-8 lens today and immediately went to mount it on my Leica 111. The lens initially begins to screw on quite easily and then the turns become progressively stiffer until it becomes impossible to complete mounting the lens with about a half turn remaining.

I have Industar 22 and 61d plus a J-12 that have no problems in this regard.

My internet research so far suggests that I may need to find someone to machine an 'undercut' or 'releif thread', if possible, to allow the lens to seat properly?

I have a Zorki 4 and not surprisingly the J-8 mounts beautifully onto this body no problem.

Can anyone help with a possible solution?

My thanks in advance.

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[jc_braconi]

I.

My internet research so far suggests that I may need to find someone to machine an 'undercut' or 'releif thread', if possible, to allow the lens to seat properly?

.Can anyone help with a possible solution?

My thanks in advance.

 

Please post a pict of the lens thread close to the end of it with the flat part

[Dez]

The Leica screw mount surprisingly used a non-metric pitch, of 26 threads per inch- I believe that was a Whitworth standard used for microscopes, Leitz's main business before they started making cameras. This is almost, but not quite the same as the metric standard 1mm thread pitch. Some manufacturers of Leica-compatible bits assumed incorrectly that the mount was 1mm, and threaded their lenses and other accessories accordingly.

 

While Russian lenses from the 50's and 60's are usually optically very good, there are not many good things that can be said for their mechanical quality control. Lenses designed for an exact 1mm thread pitch will have a range of tolerance which will have most of them fit the Leica screw mount with little difficulty, while others at the low end of the range will bind.

 

There is not a lot you can do about this problem. It is possible to re-machine the threads on the lens to fit, but this will make a mess of the threads and probably lead to cross-threading. Unfortunately the best solution may be to get another J8. In my experience, the majority will fit.

 

Cheers,

Dez

[luigi bertolotti]

Probably, it costs less to find a J8 that has a right thread, than having it machined...