Jump to content

Fitting a pocket watch crystal - which tool


Recommended Posts

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 by Chopin
Link to comment
Share on other sites

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?

P4250016.thumb.JPG.6b892611464d69ebb0401f3e8afaf1ed.JPG

 

I've got one of these...

press.thumb.jpg.dde3a612d90f412e7f74323601147d7e.jpg

 

It a cheap 'n' nasty.

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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 by Chopin
Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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

  • Like 1
Link to comment
Share on other sites

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.

  • Like 2
Link to comment
Share on other sites

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

Link to comment
Share on other sites

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.

 

Link to comment
Share on other sites

  • 4 years later...

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

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.



  • Recently Browsing

    • No registered users viewing this page.
  • Topics

  • Posts

    • Post some pictures , some good close ones of the parts you've described. 
    • Ive never used epilame H only information i have read and mentally stored about it mostly from Nicklesilver here and elsewhere ( the fork horns thing ), maybe the residue powder that is removed has some grinding effect ? So probably a good idea to limit its application areas to only the absolute necessary. Yes as far as i know epilame rubs off relatively easy, the technique of running the watch to make a groove through it first in the pallet stones where the lubrication is then placed. This i understand creates the barrier for the lube to sit up to. If i can find a good balance of pros and cons of its use then thats one process i can avoid by using a thixotropic lube on the stones. The epilame i would say allows for a more fluid lubrication to be used that would increase amplitude on low beat movements. The stearic acid powder is extremely cheap, the problem is the fuming process to coat parts, is not selective , the whole part has to treated in this method. If epilame residue can cause wear then thats not good, if I remember the conclusion was not proved entirely just a general assumption between watchmakers. The thread is out there somewhere, the same discussion is also old on a facebook group. Ive never used epilame H only information i have read and mentally stored about it mostly from Nicklesilver here and elsewhere ( the fork horns thing ), maybe the residue powder that is removed has some grinding effect ? So probably a good idea to limit its application areas to only the absolute necessary. Yes as far as i know epilame rubs off relatively easy, the technique of running the watch to make a groove through it first in the pallet stones where the lubrication is then placed. This i understand creates the barrier for the lube to sit up to. If i can find a good balance of pros and cons of its use then thats one process i can avoid by using a thixotropic lube on the stones. The epilame i would say allows for a more fluid lubrication to be used that would increase amplitude on low beat movements. The stearic acid powder is extremely cheap, the problem is the fuming process to coat parts, is not selective , the whole part has to treated in this method. If epilame residue can cause wear then thats not good, if I remember the conclusion was not proved entirely just a general assumption between watchmakers. The thread is out there somewhere, the same discussion is also old on a facebook group. If its a potential problem for amateurs to use then i would prefer not to take the risk .
    • Following on from my question about identifying screws in the AS2063 movement that basically fell out of the case in bits, I’m pleased to report that I’ve got it all back together, and the movement is running pretty well.    But… There’s something wrong with the keyless works and hand setting. It’s fine in winding and quickset date position - these work - but in hand setting position winding the crown turns the whole gear train.  I don’t really understand how it’s meant to work. It doesn’t have a traditional friction fit cannon pinion.  The second wheel is unusual with a pair of smaller pinions on it, which seem to interact with the barrel and the motion works.    Could this be the problem? I must admit I just cleaned it and popped it in place when reassembling the gear train. I’ve lubricated the pivots but didn’t do anything to the extra bits on the second wheel.    Does this make sense and is anyone able to figure out what I’m doing wrong? Thanks in advance, as always.    ETA - the parts list calls it the Great Wheel, not second wheel. 
    • You're thinking metal to jewel in general I guess. Maybe it would be a good idea to peg the pallet staff jewel hole on the main plate after the epilame treatment. I think that could work as it is my impression that the epilame doesn't sit very hard, but I could be wrong about that so feel free to educate me. I didn't remember that 9501 was thixotropic (thanks for the link). That would mean it's even runnier during impact (lower viscosity) so perhaps it's time I get some fresh grease as mine seems a bit too runny. What I have seen is a whitish surface after washing but it goes away if I scrub the surface with a brush in a degreaser (Horosolv). I don't think it embeds itself in the metal but sticks very hard to the metal. I don't worry too much about the cleaning solution. I just want perfectly clean parts and my solution can be replaced for little money (ELMA RED 1:9). Anyway, I quite often need "to strip back and rebuild" and scrubbing parts by hand isn't exactly the most stimulating part of a service. Just got confirmation that Moebius 9501 has a lower viscosity (68 cSt at 20° C) than 9504 (305 cSt at 20°). The viscosity of Molykote DX is 285-315 cSt at -25° to +125° C. I was surprised to see that the viscosity of Moebius 9010 (thin oil!) is higher (150 cSt at 20°) than my 9501 grease!
    • I’ve had a couple movements where it is clear the previous watchmaker was diligent with lubrication but the old epilam had turned to a fine white powder covering the pallet fork and keyless parts, which can’t be good for parts. I’m spare with epi since I don’t know how long it takes to degrade to that state…
×
×
  • Create New...