Just what exactly is Leica M39x26tpi mount?

[jernejk]

I need to make an adapter for my Meopta enlarger to fit el-nikkor lens, which uses the standard M39 mount.

If I understand correctly, M39 enlarger thread is really leica "M39x26tpi" thread. But what kind of thread is that? Mixing metric and imperial standards? My dad who has some general experience in the threads area says it's 26 threads per 25.4mm, so it's actually just M39x1. So why is it reffered to as M39x26tpi at all? Is it OK if I just use a normal M39 thread?

 

[darkosaric]

I use el-nikkor 50/2.8 on axomat and el-nikkor 75/4 on magnifax 3 without any problem.

 

[Aron]

The confusion might come from the fact that this thread is often written as M39, when it really is 39x26 TPI, no M. It's a Whitworth thread, with a 55 degree profile angle, only the outside Diameter of the male thread is given in mm.

I have a few lensboards made to this specification (26 TPI and not 1 thread/1 mm) and I can screw in my factory LTM lenses with the greatest ease.

 

[jernejk]

Thank you!

 

[Prarry]

http://en.wikipedia.org/wiki/M39_lens_mount

Seems reasonably comprehensive...

 

[ic-racer]

Could you buy one? http://www.fotoimpex.de/shopen/darkroom/meopta-lensboard-m-39-ax5op6.html