Lubricating stiff lens (Mir-1)
I have a Mir-1, one of the Soviet 37mm M42 models. It's a nice lens, in optically mint condition, but the focusing is very stiff.
I can't quite work out how to get in at the focusing helical.
Anyone tried taking one of these apart?
In general, there is a double helical. The lens barrel will have a coarse helical (large threads). The focusing ring will have a fine helical (tightly spaced threads).
The lens barrel's helicals also should have a long notch or cutout that keeps the barrel from rotating when focusing. This should mate with a bar or post or rigid tab inside the lens.
Note the positions of the focusing ring and the barrel when disassembling because both must be in identical positions on reassembly. This sounds more difficult than it is, although it can be the longest part of the process. Plus, you have to make sure that it is collimated. With an SLR, it should be simple.
Once apart, be sure to thoroughly clean both sets of helicals, removing all traces of old grease. Then relube and reassemble. This is best accomplished with the lens elements removed, simply because removing the old grease can be messy.