Movement case clamp torqueage

[preacher62]

This might not be the right board for this question but here it is anyway.

What is the formula for correctly tightening the case clamps on a ETA 2836 in a sub case. I have some that run great, but have found out recently that if you tighten it down you can compress the dial ring to far onto the movement and hose up the date changing and even slow the movement down.

On one that was running -10 sec/day and the date didn't change correctly, I loosened the clamp screws 1/4 turn and now the movement is running in the 1 - 2 sec range and the date wheel flips like it is supposed to.

Don't remember anyone ever commenting on this. Sometimes the bend in the clamp bar is just right and sometimes not.

Thanks!

Edited February 23, 2010 by preacher62

[HauteHippie]

I haven't seen the issue with the accuracy, but when we start tossing date overlays and what have you between the dial and the movement, the case clamp tightness can most definitely play a roll in the date flip. There has to be enough clearance. I recently had the issue on a franken datejust.

[preacher62]

Thanks for the response. I have backed the clamp screws off just to where the movement is stationary and used some blue threadlock on the screws. I think that this is a satisfactory fix.

On the accuracy...could be that the date flip is a symptom of the same problem. I'm just making this up, but I think that with the dwo mounted and the clamp tightened down too much it presses the date wheel slightly against the date change wheel under the date wheel, slowing the movement. I might be all wet on this as I have not researched it, but it could be. I think that it is on the dial side of the movement. I don't think that the clamps compress the movement, itself...that could really tear something up.

Thanks again for reply.

Edited February 24, 2010 by preacher62

[HauteHippie]

I am not really the person to answer the question, but my intuition says that if the case clamps are effecting the operation of the movement from a timekeeping perspective, then the effect would be more catastrophic than a difference of a few seconds a day... A few seconds a day can be the difference between resting the watch on its left side vs its right side overnight... if that makes any sense.

[preacher62]

I does make sense and I thought of that. Just haven't come up with a better explanation yet.

[krpster]

Why not try some dial dots between the movement and the dial? Might be enough to give you the clearance you need for the date wheel with the case clamps tightened down. I have not tried this myself, just an idea.

[preacher62]

Thanks! I've got it fixed. Just loosened the screws a quarter turn.