Resealing Watch Casebacks

[Seight_Returns]

I've had the backs off a couple of my watches recently - one of my Seikos for a battery change and my Steinhart to have a go at regulating it.

What do I need to do to ensure they're waterproof when I screw the casebacks back on ? In both case the O-rings are intact and still flexible - can I reuse the existing O-rings with a bit of lithium grease ? Or should I replace them as a matter of course ?

I don't need to preserve the full depth rating on either case - but I would like them to be safe to swim with.

[Lorne]

Whilst it's always good practice to replace the O ring (generally because they only cost a few pennies), there's no harm in reusing an old seal if it's still in good condition. Give it a close examination to make sure there are no tears or cracks, apply a very fine coat of silicon grease and it will be perfect. Don't screw the back on to the torque setting you might use on your wheel nuts though as that'll probably tear even a brand new seal.

[Fallingup]

Getting a list of manufacturers torque settings with new seals would be a holy grail for me .I'm probably guilty of over tightening case backs. You do get a certain feel for it but it's not an exact science. Of course, pressure testing is the only way to be sure but that assumes all the other seals are in good order and anyway I'm not willing to spend the money on getting a tester. Neither is it really necessary if one is not going to be using the watch to it's extremes. IMHO!

[bry1975]

Rolex always quoted 5Nm caseback tightness.