Replacing glass on a French Clock

Discussion in 'Clock Case Restoration and Repair' started by bsterlin, Sep 10, 2011.

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  1. bsterlin

    bsterlin Registered User

    Aug 25, 2011
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    I need some help replacing the face glass on an old french marble clock. It is the beveled glass that has broken and I managed to find a replacement but I can't figure out how to mount the glass. There apears to be a ring between the inside front bezel and the glass. Does anyone know how to get it out and replace the glass? Appreciate the help.
     
  2. laprade

    laprade Registered Users

    Sep 10, 2008
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    writer, radio producer, old building-materials adv
    Irish, but live in Laprade, 16390, France, (70 mil
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    The basic principle is that used to put a steel tyre on a cart wheel. The thin end of the bevel sits inside the groove on the bezel. You have to heat the bezel to make it expand, and then fit the glass, which is then held in place, when the metal cools and shrinks. Just hope that the glass maker and whoever measured the glass, got it right. I've always sent them out and let the glass makers do the job. There used to be quite a few glass fitters, but as rents soared in London, they either closed down or moved out to the sticks.
     
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  3. bsterlin

    bsterlin Registered User

    Aug 25, 2011
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    Thanks for the reply! I see this is not going to be easy. Might be easier to try and find a new door with the glass already in it on ebay or something and just replace the door. But if I did try it, once heated does the inner ring come out and then fit the glass in from the back or once heated you fit the glass in from the front?
     
  4. Talyinka

    Talyinka Registered User
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    May 14, 2011
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    It is easy enough, much easier to do than to explain :D. The glass is crimped in place, i.e. the metal rim is heated up, thus expanded, until the glass will drop in. Once the rim cools off and as a consequence contracts, it will hold the glass in place.

    If you have a hot-air gun, e.g. the type used to crimp insulation around cables, then the easiest way is to use that. Just heat the bezel evenly, around and around the rim of the glass, until you can press the glass out (use heavy work gloves of course). That the glass also gets hot is of no consequence because the coefficient of thermal expansion of the metal is so much larger than that of the glass that it compensates for the expansion of the glass.

    The second method makes use of this fact. Instead of using a heat gun just put the bezel into a large pan and heat it over the gas on your cooker. This takes longer but the end result is the same - the glass drops, or is easily pushed, out.

    Like with all processes based on thermal crimping the diameters of glass and rim need to correspond. You should check that before attempting to install the replacement glass. The method of installation is the reverse of that of removal - place the glass on top of the rim and heat the rim until the glass falls, or can be pushed, in place. Then allow to cool without disturbing - and you are done.

    The whole process takes 5 minutes.
     
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  5. aka

    aka Registered User
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    Jul 3, 2007
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    My procedure is not the correct one, but I've fitted some flat glass in a similar cast brass bezel, and the procedure can be extended to beveled glass. You sand the edges of glass with 100/200 wet sand paper, until it fits inside the bezel, then put some liquid glue to hold it. It takes lot of time and effort, but you can do it. Typically you fit the glass from the front of the bezel, and not the back.
    Ideally you should send the bezel to some glass cutting services to cut & fit it (like AA glass company).

    Thanks
     
  6. Talyinka

    Talyinka Registered User
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    May 14, 2011
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    You wrote it...
     
  7. laprade

    laprade Registered Users

    Sep 10, 2008
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    writer, radio producer, old building-materials adv
    Irish, but live in Laprade, 16390, France, (70 mil
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    To put anything other than a proper bevelled glass in a french clock, should be relegated to the hall of shame. A scientific instrument glass fitter, or an antique clock glass fitter, has the required tools and gauges to do the job properly. You have to be able to measure the inside of the convex groove in the bezel, and get the correct angle of the bevel. If you have to grind the glass, you then need jewellers rouge wheels to polish it afterwards.
     
  8. woodlawndon

    woodlawndon Registered User

    Jan 18, 2017
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    Sorry for reviving a very old thread but this is the exact procedure I need to do. I don't need to remove a broken one but put in a new bevelled glass into the bezel. Would it work if I placed the bezel on a flat, electric stove top with the heat on low/medium? I figured I could get a nice even heat around the bezel to expand it using the flat stove-top. I do have a heat gun if that method works better. Thanks.
    Don
     
  9. ClipClock

    ClipClock Registered User
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    Jun 20, 2013
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    I think your idea should work woodlawndon.

    I'll share my method, which is similar to one mentioned by Talyinka. To remove the old broken glass just push from the inside out.

    The new glass then goes in from the front (obviously). I heat the bezel to boiling point in a pan of water. Fish it out onto a soft towel and immediately (dont delay) press the new glass in firmly, you'll hear/feel when it clicks in place. I've done about 10-12 and never had a problem, but always make sure the new glass is absolutely identical in size. Good luck :)
     
  10. woodlawndon

    woodlawndon Registered User

    Jan 18, 2017
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    ClipClock;

    Just wanted to say thanks. Tried your method this morning and it worked like a dream, the glass popped right in. Not yet sure if I prefer shrink fit to clips but this went in easily. Thanks again.
    Don
     
  11. ClipClock

    ClipClock Registered User
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    Jun 20, 2013
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    Well done, glad to be of help :)
     
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