Crystal: glue or press

[LittleWatchShop]

I have posted about my Vulcain Cricket watch in another thread.  Crystals should arrive next week--one will fit for sure.

This is not a water proof watch.  Therefore, going for a super tight fit may not be necessary--dunno...open for comments.

I am thinking that I will get a nice fit and use the crystal glue that I have.  The Vulcain uses a bezel to achieve the front-loader configuration.  So, I figure, I will install the crystal that is a good-enough tight fit and then take it out and apply the glue and re-install.

Appealing to the experts on the best approach here.

[jdm]

Press in when a nylon gasket or tension ring keeps the crystal firmly in place. 

Otherwise use cement. 

[Marc]

There's no harm in using cement with a standard non-tension ring acrylic crystal, other than the potential to make a mess to clean up afterwards if it doesn't go quite right, but, assuming we're talking about round crystals, a correctly sized crystal doesn't require cement.

The rebate that it fits in to is slightly conical so that the top is fractionally smaller than the bottom. This matches the slightly tapered sides of the crystal. The diameter of the correctly sized crystal is fractionally larger than the widest part of the rebate so that once installed the crystal will always be in compression. This not only creates a tight seal between the edge of the crystal and the rebate, it also forces the base of the crystal into contact with the seat in the rebate. The design also locks the crystal in place so it can't fall out.

[LittleWatchShop]

4 hours ago, Marc said:

There's no harm in using cement with a standard non-tension ring acrylic crystal, other than the potential to make a mess to clean up afterwards if it doesn't go quite right, but, assuming we're talking about round crystals, a correctly sized crystal doesn't require cement.

The rebate that it fits in to is slightly conical so that the top is fractionally smaller than the bottom. This matches the slightly tapered sides of the crystal. The diameter of the correctly sized crystal is fractionally larger than the widest part of the rebate so that once installed the crystal will always be in compression. This not only creates a tight seal between the edge of the crystal and the rebate, it also forces the base of the crystal into contact with the seat in the rebate. The design also locks the crystal in place so it can't fall out.

Thanks.  This is very helpful.  I will aspire to a compression fit!

[spectre6000]

Since it 's already come up, I've got a rectangular crystal that needs to be replaced. Also no waterproofing promises. It came out of the case with a surprisingly light touch as if it were maybe supposed to have been glued in, but wasn't. I don't think the dial was supposed to be holding it in, but haven't confirmed this. I haven't had a chance to dig into it at all yet beyond that. Any thoughts?

[Marc]

@spectre6000 Fancy shapes (rectangular counts as fancy, basically anything that isn't round) is where your cement really comes in to its own. The shape of the crystal makes it very difficult to use the same mechanism as for round crystals , I'm not sure about ovals. But this is where I would use the biggest crystal that I can get to go into the case, but seat it on a very fine bed of something like GS Hypo cement, or one of the UV curing crystal cements.

[spectre6000]

The watch in question is NOS from the early 70's. As best I can tell, there is no indication that any glue was used from the start. As if it's relying on the notion that no one is going to be pushing it at all from behind to keep it in place. Should I interpret this to mean anything?