Watch back gasket sizing

[mmitchelmoss]

Hi gang,

I have replaced the battery in my wife's ESQ quartz watch. It has a snap back which was very difficult (for me anyway) to open.

I replaced the battery and replaced the gasket with one that was as close to my measurements as possible, using a set of calipers. The gasket seems to fit pretty well, but when I attempt to snap the case back on the gasket spooges out and now looks kind of stretched. When y'all size your gaskets do you choose the exact inside diameter to match the back or do you choose one slightly smaller so that it stretches over the back? 

Also, is there any magic trick to getting a really tight snap on back snapped back on?

Thanks all

[Ishima]

I generally aim to have a little tension in the gasket holding itself to the inside of the case back, so in other words, i'd pick one 1 or 2 mm smaller, too much smaller and the gasket will stretch thin and be ineffective but 1 or 2 mm of stretching ought to make little enough difference.

I've often found case back gaskets that didn't look stretched after i opened the watch to do just as you described, so its not unheard of, they just got degraded or agitated enough from opening to give them a touch too much slack. 

Invest in good case back press, that's my only advise for tight case backs, the way  modern watches are made now means even basic fashion manufacturers are able to make incredibly tight fitting case backs and it's just no longer realistic to expect to be able to work on watches and close them just with your bare hands. 

Edited March 15, 2017 by Ishima

[RyMoeller]

Since gaskets are pretty cheap I usually get the exact size and also a size or two smaller.  I've encounter the same problem though as a result of the gasket being too thick.

[Neileg]

I agree with Ishima. A smear of silicone grease can help if things are tight.

Cheers, Neil

[mmitchelmoss]

Thanks y'all. I will try sizing them a tad smaller in the future. I will also try a bit of grease to see if that helps. Coming from a woodworking background, I do have some parallel jaw claps that I may try to use to press the back on. It has already come in handy for pressing in a bracelet pin that I stupidly pushed partially out the wrong direction.

[SSTEEL]

8 hours ago, RyMoeller said:

Since gaskets are pretty cheap I usually get the exact size and also a size or two smaller.  I've encounter the same problem though as a result of the gasket being too thick.

Depends, from experience, I originally purchased various sizes lots from China, BIG MISTAKE, they perish over time, become brittle, and frey.  So I binned the lot and purchased the more expensive option boxsets Swiss ISO type thick from cousinsuk.  Its not worth risking a watch water resistance with anything else to be honest.

I find the £52GBP box assortment very good quality.

https://www.cousinsuk.com/product/o-ring-box-sets

Edited March 16, 2017 by SSTEEL