Industar collapsible won't mount on Leica IIIc

[jamesmck]

I have a 1963 Industar-50 collapsible that will not screw in all the way on my Leica IIIc (whether extended or collapsed). There's about a mm space between the lens flange and camera body after it is as tight as I dare, and, of course, it will not focus properly. Nothing is hitting anything on the outside. It threads in smoothly most of the way, and then stops. The lens fits fine on my Fed-2 and Zorki-4. Thanks for any thoughts.
-- James --

[Brian Sweeney]

"It Should Work", sometimes the threads get damaged ever so slightly, and a lens will refuse to mate with a body. I keep a Canon LTM mount to try to straighten out threads. Sometimes it works.

My I-50 fits perfectly on the Leica cameras, just verified that on my Leica IIIc (converted to IIIf). Look all the way around the lens mount, some slight deviations in the threads towards the end. I've seen this prevent a lens from screwing in completely.

[jamesmck]

Brian: The threads appear good, and I just ran a thumbnail through them and can feel no irregularities. As I mentioned, the lens mounts OK on a Fed-2 and Zorki-4. I just tried it on a Bessa, and it fits fine there, too. I guess I have either an odd Leica IIIc or an odd I-50. I've had several other FSU lenses (non-collapsible) on the Leica with no problem. Puzzling.

[John Robertson]

I had this with a Canon 7s a few years ago, some of my Leica and FSU lenses tightened up as you screwed them in. I think that these things are made to certain tolerances and in this case all the tolerences were incompatible. don't force it what ever you do.
My Collapsible Industar 50 (made 1960 ) fits my Leica 11, Bessa R2 with adaptor, (Leitz make) and Fed2 just fine. Probably just bad luck
No consolation but as they say sh** happens.

[Brian Sweeney]

Probably a case of tolerances adding up against the combo, as mentioned above. I get some of these, but more often in Contax/Kiev/Nikon S-Mount than on the Leica.

[Keith]

Run a straight edge or similar over the flange surface of the IIIc and check for distortion ... I had the same thing happen a while ago on my II. Turned out there was a small piece of covering trapped under the edge of the flange distorting it slightly on the camera body.

It effected some lenses and not others oddly!

[jamesmck]

Thanks for the suggestions, everyone. I examined the camera (and lens) threads and flange carefully, and nothing seems amiss. I think I will just live with not using this lens on this camera.

[Steve M.]

I would try a spot of dry bike chain lube or a similar non petroleum oil on the threads and see of that helps. The lube will prevent it from seizing. Just give it a little more firm pressure at the stopping point. There's either a spot on the threads that needs a bit of help getting over, or that particular lens is defective (in regards to mounting on your camera).

[Dave Wilkinson]

Originally Posted by Brian Sweeney

Probably a case of tolerances adding up against the combo, as mentioned above. I get some of these, but more often in Contax/Kiev/Nikon S-Mount than on the Leica.

agreed, and it is not generally known that the Leica thread mount (as friend Roger often points out) is actually 39mm dia. X 26tpi pitch, tpi (threads per inch) being the old English imperial way of thread pitch measurement, not as would be expected - 1mm pitch, which is the measurement between 'crest' (or 'valley') of the thread when viewed from the side - vvvvvvvv. Don't ask me why this is so, but there is a very slight difference, often accomodated by slight machining differences. For this reason - when I am generating these and similar threads on the lathe, I like to have the mating component to hand - for trial fit, as a part will often fit smoothly in one camera or lens, and bind slightly - in another!
Cheers, Dave.

[Rob-F]

Since, by your inspection, there is no damage to the threads on the lens or camera, it occurs to me the thread pitch on the Industar could be a little off, causing it to bind at the last turn. I know that seems unlikely, but apparently everything else has been ruled out!

Edit: Oops-Guess I missed Dave's post. I think he has covered that point.

[Dave Wilkinson]

Originally Posted by Dave Wilkinson

agreed, and it is not generally known that the Leica thread mount (as friend Roger often points out) is actually 39mm dia. X 26tpi pitch, tpi (threads per inch) being the old English imperial way of thread pitch measurement, not as would be expected - 1mm pitch, which is the measurement between 'crest' (or 'valley') of the thread when viewed from the side - vvvvvvvv. Don't ask me why this is so, but there is a very slight difference, often accomodated by slight machining differences. For this reason - when I am generating these and similar threads on the lathe, I like to have the mating component to hand - for trial fit, as a part will often fit smoothly in one camera or lens, and bind slightly - in another!
Cheers, Dave.

Reading the op again - it would seem that with approx. 1mm gap remaining, that the last two or three threads need 'chasing' (as machinists call it)- it might possibly be remedied by the careful use of a thread file.

[jamesmck]

Using my index-fingernail as a test instrument (!), there don't seem to be any irregularities in the threads, other than a bit of dark gunk here and there in the bottom of the VVV. I'm going to try cleansing the "valley" of the threads with a bit of string moistened with Ronsonol. But, I will be without the IIIc for a couple of weeks due to the need for some unrelated tuning, so it will be a while before I can see if this helps. Thanks again for the suggestions.

[jamesmck]

Well, I've thoroughly cleaned the lens threads, to no avail. I guess this particular I-50 is not meant to have the pleasure of working with this IIIc.

[xayraa33]

I have had the same problem with a certain collapsable coated(Fed) Industar 10 lens.
It will not mount on any LTM Leica or Canon camera but fits fine on a Nicca/Tower or any Zorki or Fed body. The lens lives on my Tower 3 body now.

[Santafecino]

Well--I'm a latecomer to this thread, but is there a chance of a bind between the lens body and the rangefinder follower?