First time - Fitting new glass to pocket watch

[Boydie]

Hi all, I’ve been working on wrist watches for the last 2 years. I’ve been asked by a friend if I can fit a new glass to a pocket watch he picked up at a car boot. It doesn’t have one at the moment. The Recess is just 0.5mm deep and 38.9mm diameter. It’s an old watch, any idea how old? And how do I purchase a dia 39mm glass and press using a normal press as for a wrist watch? I have a cousins account. Any advice on the type of glass shape (dome or flat etc), size, material to make it look like it should for its age and of course fit well and stay in place? Thanks I’m advance. Boyd.

[oldhippy]

Post a photo of the movement please. I know it seems daft but by seeing the movement it will help me to give you advice on the type of glass. 

[KarlvonKoln]

I second OH's request; nice clear photos are amazingly helpful.  So far, it sounds like about a size 6s.  And I see the size #4 key back there.  I'm wondering if it could be a little Swiss cylinder ebauche.  Too early to tell yet, though.
Crystals have to be very carefully measured out.  Even with an open-face crystal, one needs to know more than just the diameter, there is the thickness to consider, and whether it need be "domed" to allow for clearance with the arbor and hands.  Sometimes, we recognize a kind of movement from the photo, and often can reference the serial number, and just know what to tell about it.  So absolutely, let us admire some pictures of it's movement.

[oldhippy]

4 hours ago, KarlvonKoln said:

  I'm wondering if it could be a little Swiss cylinder ebauche.

Same here. 

[Boydie]

10 hours ago, oldhippy said:

Post a photo of the movement please. I know it seems daft but by seeing the movement it will help me to give you advice on the type of glass. 

Thanks for answering. Attached movement photos. It’s engraved Leumas. 

[oldhippy]

That is a five bar movement with a cylinder escapement, also it is open face so the glass would be quite thick. This is the type you need and it should be glass not plastic that is if you want it to be like its original. Here is what you need. Make sure all dirt is cleaned from the bezel where the glass fits. Measure from 12 to 6 or 9 to 3 for the diameter, if you can't get the exact size you go for the size down you will need to get the proper cement to hold it in.  The red arrow one is the type to get.

 

[KarlvonKoln]

Old Hippy knows.  If you live in the UK, I would turn to Cousins.  If you live in the United States, there is Ofrei Watch (Otto Frei) and Esslinger.  As OH shows in the pic, the crystal is domed just on the inner surface to allow extra clearance.  Good luck with it.  I'm going to do a bit of research on "Leumas", because that's a pretty movement.  And the engraving on the balance cock is just gorgeous.  I like that one often finds these little silver cylinder watches with beautifully painted dials too.  The way they used to decorate even some of their more common watches is just a cheerful thing to me.  These days, it seems like so many things out there are so stark and utilitarian, whereas back then it was taken for grated that one must decorate all manner of devices, tools, appliances, architecture, and of course watches.  *sigh* I was born in the wrong time period.

Edited February 3, 2022 by KarlvonKoln

[Boydie]

5 hours ago, oldhippy said:

That is a five bar movement with a cylinder escapement, also it is open face so the glass would be quite thick. This is the type you need and it should be glass not plastic that is if you want it to be like its original. Here is what you need. Make sure all dirt is cleaned from the bezel where the glass fits. Measure from 12 to 6 or 9 to 3 for the diameter, if you can't get the exact size you go for the size down you will need to get the proper cement to hold it in.  The red arrow one is the type to get.

 

Many thanks guys! Cement, is G-S Hypo ok? I’ve got but never used, any a dice on how much to put on? Diameter is 38.9mm so is this the size I purchase from Cousins? Spot on, 0.1mm over or under? The recess is only 0.5mm this seems small for cement and glass, thoughts? Would mineral glass be right? I just checked Cousins online and I have their catalogue, but I couldn’t see the right shape glass that goes up to this size. Any help appreciated. Picture of back of case included. 

[oldhippy]

Get the nearest to the size you need here.

 https://www.ofrei.com/page778.html

[KarlvonKoln]

In olden days, the crystal would be a fraction of a millimetre too large to just press in, by intent.  The bezel would be heated until it had expanded enough to accept the crystal, which was then carefully and quickly put in place, and all was allowed to cool back down slowly.  I have done this with great success a few times, but it is not always ideal in all cases.

That said, for cementing crystals I use the clear UV-hardening resin.  GS Hypo is great stuff, but I think the UV resin has greater strength.  It seems to work well when something heavy, like a mineral glass, must be bonded to something firmly, and both surfaces are extremely smooth.

[Boydie]

20 hours ago, KarlvonKoln said:

In olden days, the crystal would be a fraction of a millimetre too large to just press in, by intent.  The bezel would be heated until it had expanded enough to accept the crystal, which was then carefully and quickly put in place, and all was allowed to cool back down slowly.  I have done this with great success a few times, but it is not always ideal in all cases.

That said, for cementing crystals I use the clear UV-hardening resin.  GS Hypo is great stuff, but I think the UV resin has greater strength.  It seems to work well when something heavy, like a mineral glass, must be bonded to something firmly, and both surfaces are extremely smooth.

Thanks!