Leica screwmount thread wear?

Aristotle80 · Aug 5, 2013

Hey everyone. I recently joined the Leica screwmount camera club. I shoot them on a new Voightlander body though.

My question is about wear to the screw threads. I have more than one lens. I'm always very careful when I screw them on and off, no rushing, forcing, or overtightening. If I exercise care when mounting and unmounting a screwmount lens, should I have concern for wearing down the threads? Can I assume that the metallurgy of the threads can handle that wear, or should I keep lens changes to a barest minimum?

Sorry if this sounds like a silly question, I am mostly used to using bayonet mount lenses.

GRHazelton · Aug 5, 2013

Somewhere I remember reading that screwmounts are much more tolerant of wear, since the final position of the lens relative to the film plane is determined by the seating of the lens as it is tightened. Wear on the face of the lens mount is unlikely. With a bayonet mount there is the chance that the segments of the mount, for lack of a better word, will over a long time, wear and thus the lens will not be tightly registered to the face of the lens mount. I've yet to read any posts anywhere commenting on either bayonet or screwmount wear. I suspect that the concern is mainly theoretical. Certainly you don't want to overtighten anything on any camera!

Anyone else have thoughts on this?

Tom1956 · Aug 5, 2013

Think about a piston in the cylinder. I'll bet it moves more times than you will ever change lenses.

GRHazelton · Aug 5, 2013

Tom1956 said:
Think about a piston in the cylinder. I'll bet it moves more times than you will ever change lenses.

Well put! And we don't have to worry about changing oil in our cameras.

Xmas · Aug 5, 2013

four things to consider
- avoid cross threading do not use any force when searching for thread entry
- clean the cameras and the lenses threads occasionally
- when fitting lens dont knock the focus follower cam
- some of the FSU lenses have aluminium mounts be more careful

the screw mount should give less problems than the bayonet it is just slower

Aristotle80 · Aug 5, 2013

Thanks! Terrific.

Gerald C Koch · Aug 5, 2013

The Leica lens mounts are chromium plated brass. That being said any wear will NOT cause any focusing problems.

Nathan Riehl · Aug 5, 2013

At least plastic bits aren't a thing to worry about. I picked up a Pronea 6i body for the sake of using up a bunch of APS film I found for super cheap and the lens it came with (28-70 IX) had 2/3 of the plastic bayonet mount ripped off and somehow I didn't notice until after I bought the thing. I'm just thankful I can use the rest of my F-Mount lenses on it.

250swb · Aug 5, 2013

As others have said nothing can go out of adjustment with wear to the threads. It is the lens flange that determines the focus distance, and as this can't wear, or only minimally over many decades, so it hardly matters if the threads are sloppy (which I've never come across), just so long as they can tighten up. But the brass threads on many Leica lenses are self lubricating anyway, so even if any chrome plating wears through it doesn't matter, even at the age LTM lenses are now they will still see you out.

Steve

Xmas · Aug 6, 2013

With your Bessa there are some lenses you should not mount:

the FSU J12 36mm
the similar Zeiss prewar Biogon
physical damage to shutter

the FSU Russar dont think this fits ie mounts

some of the Kobalux wides 21 & 28mm also may not fit and their clones ditto

A Canon LTM body would have similar incompatibility problems.

Dr Croubie · Aug 6, 2013

So if the lens-flange face wears down over time, then eventually the elements will come microscopically closer to the film flange. But that is offset by the fact that the rangefinder flange also comes closer to the film at the same rate, so it all evens out in the end. Except that at 'infinity' on the lens may be past infinity, but other things being equal the rangefinder will still be accurate.

I'd be more concerned about the rangefinder cam and/or the flange on the lens getting worn out. Mount and unmount all you want, just don't change focus too often!

Gerald C Koch · Aug 6, 2013

Dr Croubie said:
So if the lens-flange face wears down over time, then eventually the elements will come microscopically closer to the film flange. But that is offset by the fact that the rangefinder flange also comes closer to the film at the same rate, so it all evens out in the end. Except that at 'infinity' on the lens may be past infinity, but other things being equal the rangefinder will still be accurate.

I'd be more concerned about the rangefinder cam and/or the flange on the lens getting worn out. Mount and unmount all you want, just don't change focus too often!

??? Your post makes little sense to me. For example, what do you me by the "rangefinder flange" There is a flange on the camera body onto which the lens sits.

Newt_on_Swings · Aug 6, 2013

Nope, these lenses are threads are pretty hefty, as long as you never force a lens on, or try to force on a lens with damaged threads you should be fine. Also to reduce stress on the rangefinder cam, I always thread my lenses on with them set to the closest focusing distance. Its a good habit to pick up. I also store my lenses like that as well, with plastic rear caps screwed on and focus to closest.

Dr Croubie · Aug 6, 2013

Gerald C Koch said:
??? Your post makes little sense to me. For example, what do you me by the "rangefinder flange" There is a flange on the camera body onto which the lens sits.

What I meant was the bit on the lens that contacts the rangefinder cam in the body. On some of my lenses it's an entire ring around the inside of the lens that rotates when it moves closer to/from the film, on others it's a ~1cm-wide bit of metal that just moves in and out to move the rangefinder cam.
My reasoning is that if the mounting flanges on the lens and/or camera wear down, then the lens screws on a bit farther each time, the elements are closer to the film so go 'past' infinity, but the rangefinder cam is also pushed the same distance, so it all evens out.

(but yes, my post wasn't meant to make sense. Translated, it means you can either not use your lenses, miss shots because you've got the 'wrong' lens on, and keep them in useless pristine condition, or you can use them as intended and not worry about some minor wear and tear that may result from taking great shots...)

Gerald C Koch · Aug 6, 2013

Much clearer now. There is usually an internal adjustment within the lens that can be used to correct for any wear.

Xmas · Aug 7, 2013

The lens cam follower in the camera in the Leica and clones is a little wheel that rotates when you focus a lens so the wear over decades of hard pro use is imperceptible unless the wheel jams.

Only the Russians did not copy the rolling wheel.

The chrome plating on the cameras registration datum only sees a few degrees of contact as you tighten the lens. On a strip the technican needs to shim the datum to the registration distance as he rebuilds.

The long base rfdr are good for f/0.95 lenses the short base Canon VI ok for /1.2...

E. von Hoegh · Aug 10, 2013

Tom1956 said:
Think about a piston in the cylinder. I'll bet it moves more times than you will ever change lenses.

Or the watch in my pocket, which was made the year the Titanic had that mishap. Five ticks per second, and lets say it's only run half of those 101 years...

Leica screwmount thread wear?

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