i put a very small amount of Vaseline from my finger on the M42 screw-thread; it makes it smoother to change the lens and does not wear the metal mount -- do any others here do it ? Is ot advisable ?
I've never done it, but if I were to, I would keep it to a minimum. I would try to put an almost indescernable film on them. I've used vaseline for a lubricant for many years.