Does anyone have an explanation for the self-loosening situation with hand nuts? The nut tightens by turning it clock-wise and the hands turn in the same direction, so the nut should stay tight. I have noticed this in some modern German movements I have. What weird law of Mechanics applies here? The only way I could stop one from loosening itself each week after it was wound up was to spply some LocTite; that kept the nut in place.

I'm a clock novice, but as a mechanical engineer, I know something about mechanical fasteners. As the hands are turned thru the rotation of the center post, in a series of short clockwise jerks from the movement, the inertial of the hand nut will tend to resist each of those movements with a counter-clockwise reaction, which will loosen it in time.

Another way of locking that nut would be to tighten down a second nut on top of it. That will prevent it from loosening by acting as a mechanical lock.

Ed,
Thanks! That is a very good explanation.

Usually a hand washer will do the trick.