Fitting a pocket watch crystal - which tool

[p2n]

What is the best tool for fitting this crystal? I've got a lift tool, but this crystal seems too thin for that to grip.

 

[Chopin]

Sometimes a special transparent (such as hypo gs) cement can be/was used for fitting certain types of glass on certain types of cases/bezels.

First of all those claw like lift tools do NOT work on mineral glass. They work on acrylic which is more elastic than mineral.

You're supposed to press fit it (if it fits that is). As I said, some jeweller's cement might be necessary if it's a bit smaller or if for some reason it wiggles around or rotates/moves around.

You would have to use a watch glass press for this one if it's a tad larger.

Edited April 25, 2018 by Chopin

[p2n]

I got two sizes of glass just in case.

The bezel has an overhand/lip so I though the crystal would need to be compressed/distorted to fit?

 

I've got one of these...

 

It a cheap 'n' nasty.

[Chopin]

What if the original glass was acrylic ? What if the watch was sort of made with an acrylic crystal in mind ? What watch is it ?

[p2n]

I don't know what the original was - it was missing when I got the watch.

[jdm]

35 minutes ago, p2n said:

I don't know what the original was - it was missing when I got the watch.

You need to fix with cement, glass won't work as "friction fit" without a nylon gasket, as it will break.

[p2n]

13 minutes ago, jdm said:

You need to fix with cement, glass won't work as "friction fit"

So a glass that is slightly smaller?

[jdm]

3 minutes ago, p2n said:

So a glass that is slightly smaller?

Yes, as in going in and out with no effort.

[p2n]

I'm building up quite a collection of bits that don't fit lol. Oh well.

What sort of cement should I use? I don't have a UV source so can't use that.

Would this suffice? https://www.cousinsuk.com/product/gs-hypo-cement

 

[Chopin]

Yes that is the one. I would say you could also use acrylic but I'm guessing the original one, given the age, may have used glass.

Careful not to buy one that is TOO small. Just enough so that it'll fit in there.

Edited April 25, 2018 by Chopin

[RyMoeller]

Aren't some of these old crystals fitted by heating the bezel?  Maybe I dreamed it up, but I thought pocket watches with mineral crystal glasses required the bezel to be heated in order to expand the opening to accept the crystal.

I haven't done many pocket watches so forgive me if I'm leading us astray here.

[Chopin]

I think I've heard of that but using that type of transparent cement is kind of like the same thing if you ask me...

[Marc]

9 hours ago, RyMoeller said:

Aren't some of these old crystals fitted by heating the bezel?  Maybe I dreamed it up, but I thought pocket watches with mineral crystal glasses required the bezel to be heated in order to expand the opening to accept the crystal.

I haven't done many pocket watches so forgive me if I'm leading us astray here.

Not dreamed up at all, that is exactly how they should be fitted.

Do NOT try to press it in, it will just break, particularly if it is a bevelled edge crystal.

You could use a smaller crystal and cement it in but this is a compromise for an under-cut bezel; the degree of the compromise depending on whether the crystal has a bevelled or 90 degree edge.

The correct approach is to use a bevelled edge crystal that is slightly too big to drop in, heat the bezel so that it expands, drop the crystal in place and when the bezel cools down and contracts it should be a nice snug fit so that the crystal doesn't rotate in the bezel.

crystal fit.pdf

[p2n]

Maybe an obvious question - if I heat the bezel - how hot? Hot/boiling water, soldering iron, hot plate?

[Marc]

TBH I've always just used a small electric hot plate. Lay the bezel on it and keep trying the crystal until it fits, then switch off and let it all cool down slowly. I've never measured the temp.

However, a quick Google search turns up this site;

https://www.engineeringtoolbox.com/linear-thermal-expansion-d_1379.html

If I'm using it right then it looks as though heating a brass bezel from 20C to 200C should give you just over 1mm expansion across the diameter of a 35mm bezel aperture.

[jdm]

12 hours ago, p2n said:

I don't have a UV source so can't use that.

A nail varnish drier is very cheap on Ebay or AliX. Or buy the lamp only and do your own enclosure.

[TimFitz]

The sun is the best UV source of all

[zebulon]

be gental and do not flex if its not cut to proper size. should just lay in then use you U V glue only need tool for acrylic

[jdrichard]

I really hate to admit this but I have found that a bead of lock tight glue works better than GS Cement for glass crystals that are not friction fit. I do agree with Mark on his recommendation (now doing the "I'm not worthy" hand gesture), however, i have tried all of these glues and the lock tight glue works and also cleans up nice if you have a future issue. I would recommend getting a acrylic crystal and fitting it with your cheap tool. I bought a GS Tool which works like a charm.

Sent from my GT-N5110 using Tapatalk

[syfre]

If your glass is a little larger than the bezel (says something like a few 1/100 mm) you can try a ... kitchen pan ..... heat the bezel and with the metal extension the glass will fit.

There is a vintage tool to do that, look here : http://www.daveswatchparts.com/pwcrystals.html

[p2n]

I did try with a hot plate - not sure what temp it got to but it was too hot to touch. I think the crystal I got is a little too large so ordered the next size down.

 

[Shane]

I would think that you should be able to leave the  glass "crystal" on the bezel letting them both get hot together.  Glass has a very low coefficient of thermal expansion in comparison to most other materials.  This may reduce the risk of cracking as the temperature of the glass quickly changes when dropped into the hot bezel. The difference and rate of change may be to high for the glass.  When the glass drops in, turn off the heat and let them both cool very slowly.  Not sure about an actual crystal crystal.  If anyone knows about this, I would appreciate their correction or corroboration.

Thanks

Shane