I finally hit the estate sale lottery and found a Leica 35mm screwmount lens for $1 in minty condition. In order to shoot it I bought one of the new Cosina made Voightlander bodies.

It works great and I like the results, but to sort of "round out" my lens selection I bought a 50mm screwmount lens.

I love using both lenses, but I'm not sure how quickly the threads wear out on the mount. Should I avoid switching lenses too much, or is the usual slight friction of mounting the lens nothing to worry about? My other interchangeable lens cameras are all bayonet mount so I'm not sure.

I change them all the time, even though I have 3 different bodies. One kind of film in each - b/w, color, transparency.

I smear a very small amount of Three-on-One Oil around the mount with my finger and that lubricates it well, and the lenses screw on very sweetly.

Good morning, Aristotle;

Like Pete, I also have screw mount lenses, mainly in M39, M42, and C-mount, and, like Pete, I also use just a little (emphasis on that "little" part) of a light oil on the threads to insure that there is minimal friction with the threads when I am mounting or unmounting them, although I usually use a light silicone oil of about 50, 100, or 200 centistokes viscosity. I have gotten it from some obscure suppliers, but e-Bay is becoming an easier source. My main justification for using it is that it is only oil, very much like a "machine oil," and there are no other chemicals in it that can cause some problems in this application as there might be when using the commonly available car or truck motor oil from a regular automotive supplier.

Enjoy;

Ralph
Latte Land, Washington