Domed and flat mineral crystal fitting

[MikeAdvicePI]

Do you fit a domed mineral glass crystal in the same way as you fit a flat one, by pressing it into an I gasket? 

[evn137BANNED]

Be careful. Flat mineral crystals sometimes have gasket that go on the outside around the perimeter of the crystal as the crystal has a ridge and the gasket has a depression specifically for the ridge of the crystal. In other words, it can only go on one way. I'll send a close up picture of flat mineral crystal and its gasket. Currently out of town. Will upload tomorrow.
What watch are you working on ?
Close up pics are helpful.


Ed

[MikeAdvicePI]

I've fitted flat crystals and I know what you mean (but pictures are always useful on a forum). What I'm asking is does a domed crystal usually fit with a gasket like a flat one does?

What raised the question was noticing that Cousins links to I gaskets from the bottom of their flat crystals page but not from the domed crystals page. That may not be meaningful at all, but I thought I'd ask. The domed crystals in other watches appear to have a gasket.

I'm tidying up a small Mondaine Swiss railway watch with a beaten up case and a flat scratched and cracked crystal. The idea of a slightly domed crystal for a change crossed my mind.

[Brian3]

I've seen them both used with a gasket and cemented in only, in your current case with the Mondaine I'd order a domed crystal the exact size and cement it in, done correctly it's always     a nice outcome.

Look forward to seeing the finished job.

[oldhippy]

You should always fit the correct glass and have the correct tools to undertake the task.

[MikeAdvicePI]

No worries on that score, Old Hippy. Got everything I need 

 

[Stoo]

Perfect tools for the job there Mike! 

[evn137BANNED]

Here is a pic of mineral crystal (sideways showing ridge) and gasket ( with human hair next to it for size reference ) showing ridge for crystal.


Ed

[MikeAdvicePI]

I forgot to update.

Thanks for the input, Ed.  Your crystal looks to be a particular type.  Mine was a standard slightly bevelled top and bottom glass.

The watch had been damaged when the previous owner fell and scratched the bezel and glass.  I attempted to polish the glass a few years ago, but it cracked with heat before I could finish the job.  I ended up with brass showing on the bezel, a haze on the crystal and a major crack.

Now that I've got interested in fiddling with watches, I thought I would do the easy thing and replace the glass.  First I pushed out the old one and polished the rest of the chrome off the bezel with various grades of MicroMesh. I left the deepest scratches.

I measured up the glass and ordered three glasses and matching gaskets from Cousins, one the measured size and one each of the size above and below. There's a difference of 0.7mm between the gasket and the glass.  My first choice was a 29.6 gasket and a 28.9 glass. It installed very easily and came out again just as easily, so I used the larger size gasket and crystal. I used a cheap (£12) crystal and case back press to do the job. What a difference it makes to have a brand new crystal! The press was handy again for replacing the snap-on back.

To finish off I replaced the battery, regreased the seals and fitted a cheapo strap. I didn't need to use the hammer at all.