M39 to l39 mount

[donald_miller5]

Lots of questions today. (Need JDM unfortunately for this one) Is the a conversion mount to use an m39 lens on a L39 body? Is it just a matter of changing the back focal length?

[Jochen_S]

<p>SLR lens on RF body? - yes. also make sure both share the same non metric thread and bear with being limitted to zone focusing since the SLR lenses have no RF coupling cam.</p>

[rogerwb]

<p>The thread is not identical. M 39 (mostly Russian) is a metric 39 x 1 mm pitch, while the Leica is 39 (metric) to 1 mm Whitworth pitch.</p>

[donald_miller5]

This one screws in quite easily into a Zenit 3 and the Fed 4. The mirror on the Zenit does not travel far enough when

winding to stay locked down. If I give it a little assistance it will click down. What is interesting is that depending on its final

resting point I find the focus distance any where from accurate to fuzzy and way off. I hope it is just a minr maintainence

issue. But it would be nice to use this les on a rangefinder also.

[john_shriver]

<p>Leica thread is strange -- 39mm thread diameter, but 26 turns per inch. (Rather than the 25.4 turns per inch that a 1mm pitch metric thread would be.) Either they didn't have metric lead-screws on their lathe, or they were just messing with people trying to make lenses for "their" mount.</p>

[winfried_buechsenschuetz1]

<p>"Either they didn't have metric lead-screws on their lathe, or they were just messing with people trying to make lenses for "their" mount."<br>

I think both assumptions go to the wrong directions. Leicas were designed and built in Germany which was all metric back then (or, to be precisely, after 1870 or so when the metric system was introduced on german territory), so probably lathes with metric lead screws were widely available. Probably many lathes also had lead screws (or gears for the lead screws) for non-metric dimensions (they were still in use, see below), and it would have been no big problem for others to make lenses for the L39 mount. <br>

On the other hand, mechanics still used non-metric thread dimensions back in the 1920s. Larger threads for plumbing tubes and bearings often had non-metric dimensions, and so it was not uncommon to use a non-metric dimension for the thread pitch. </p>