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Thread: Thin acrylic crystal replacement ??

  1. #1
    Grand Master sundial's Avatar
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    Thin acrylic crystal replacement ??

    My ultra-thin Vacheron & Constantin needs a new acrylic crystal



    Crystal edge is very thin and impossible to use a crystal lift to compress and fit

    And not sure exactly which type of crystal to use … checked Cousins options and found them confusing









    Can someone possibly advise:

    1) Type of crystal required

    2) Safe means of fitting.

    Currently only have a a regular type of crystal lift which cannot grip 'thin edge' crystals. Do I need another tool?

    BW

    dunk
    "I know not how to abstain from reading" … Samuel Pepys

  2. #2
    Craftsman
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    Does the crystal fit directly into the case?
    If so then it is possible to fit by slightly expanding the case :)
    Last time I did that was with a pocket watch, with a similar “knife edged” crystal.
    Get an old skool 60w light bulb and a pair of leather gloves - garden ones will do.
    Put the case on the light bulb and turn on.
    Leave for a while, can’t remember how long, but 5 or 10 minutes should do.
    Remove from bulb with gloves and place glass into now larger hole.
    As it cools it will shrink and hold the crystal securely assuming the correct size.

    Dave

  3. #3
    Master Webwatchmaker's Avatar
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    The crystal is fitted correctly by using a glass press. A domed rubber die fits inside the glass with a larger plastic die around the outer edge of it. The glass is then gently domed upwards to reduce the outer diameter. Bezel is placed underneath the domed glass and the pressure of doming released. The edge of the glass then fits into the groove of the bezel. I can do this for you. Don't heat anything !

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  4. #4
    Craftsman
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    Not paying attention. Acrylic not glass...
    Heat bad for plastic
    The pocket watch crystal was glass
    Dave

  5. #5
    Master Webwatchmaker's Avatar
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    Quote Originally Posted by Dave S View Post
    Not paying attention. Acrylic not glass...
    Heat bad for plastic
    The pocket watch crystal was glass
    Dave
    I have always fitted domed and bevelled glass crystals by hand. It takes strong fingers to clip the glass in firmly and one or two can break if you're not careful. I would never heat the bezel. Far too risky and the glass can easily crack as the bezel contracts.

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  6. #6
    Craftsman
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    Guess my lack of training. I have always regarded glass as fragile with a brittle failure mode. Gently warming on a lightbulb is quite controlled (in an engineering sort of way) and then the interference fit goes away.
    Still always learning :)

    Dave

  7. #7
    Master Webwatchmaker's Avatar
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    Quote Originally Posted by Dave S View Post
    Guess my lack of training. I have always regarded glass as fragile with a brittle failure mode. Gently warming on a lightbulb is quite controlled (in an engineering sort of way) and then the interference fit goes away.
    Still always learning :)

    Dave
    Me too !
    I don't know if you would remember Benford & O'Shea ? They were a very long established watch parts dealers in Soho. Closed in the late 70s. I guess it's now a Strip joint. The manager there showed me how to fit these old bevelled glasses and could press them in really tightly using fingers and thumbs.
    Here is one of my drawers of crystals from a cabinet full I bought from them:


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  8. #8
    Grand Master
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    I usually fit acrylic glasses like this using fingers and thumbs, warming the acrylic slightly makes it more flexible, but it’s more about technique and determination. I sometimes end up ordering 3 glasses and using the one that fits best.

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