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  1. #1
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    Default Proper Watch Crystal Size

    New member here, so I thought I would give this forum a try with a question I have about my Hamilton pocket watch. I need to replace the crystal on the watch. The watch is 16s in a Dueber case. I was able to get the old crystal out and measure the diameter = 1.664" (42.27 mm). The bezel opening = 1.663" (42.24 mm). Each of these measurements are an average of a number of measurements taken at each location. With that, I think I need a crystal size 18 12/16 which is about 1.667" (42.34 mm). That makes the crystal about 0.004" more than the bezel opening. I've heard the bezel needs to be heated up (expand) to install a crystal.

    The current crystal has a beveled edge and a slight dome. The Hamilton watch serial number puts it circa 1915.

    Is the 18 12/16 crystal the right size for the bezel based on my measurements? What brand, type, crystal should I be looking for, ie. Mi-Chevee other? Should the crystal have a beveled edge, have a low dome? Thank you

    Tom

  2. #2
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    Default Re: Proper Watch Crystal Size (RE: TomR)

    Hi Tom,

    There is only one real correct way to replace a crystal--is to locate the correct size crystal and snap it in after cleaning out the bezel properly.

    The problem with many fittings by size is that different brands of crystals do not measure the same.

    Send your case or bezel to a qualified crystal man--try Byran or Brian here on this MB. Hopefully one or both will spot this thread, or pm me for their email addresses.

    Good luck.

  3. #3

    Smile Re: Proper Watch Crystal Size (RE: Jon Hanson)

    Hi Tom:

    Welcome to the NAWCC American Pocket Watch Message Board!

    It may be helpful for you to take a look at the Crystal Replacement Wiki article.

    Good luck,
    Kent
    That guy down in Georgia

  4. #4
    Registered User Scott Erholm's Avatar
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    Default Re: Proper Watch Crystal Size (RE: Kent)

    Having read everything at my disposal, including the well-written wiki article on crystals, I still get confused about crystal sizes.

    There seem to be a few different measurement systems, and most of the time I will see two or three numbers on the original label of a NOS crystal.

    Attached is an example that makes no sense to me. It has two numbers, neither of which seem to be right. The crystal itself measures 1.516", and if I cross-reference that to the chart given in the wiki article, that would be a 17 1/16 size. However, the label has sizes 18 5/16 and 17 5/8 on the label! What's the deal?

    Thanks,

    Scott
    Attached Thumbnails Attached Thumbnails CrystalMeasure.jpg  

  5. #5
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    Default Re: Proper Watch Crystal Size (RE: Scott Erholm)

    decimal size and crystal size..................

    The size is the size--the mic size and the bezel size are equal.

    The crystal is a SIZE. Thse who are very familiar with size use the top number when replacing crystals.

    The correct way to "replace" is to use a crystal gauge to measure the old/ replaced crystal which matches the top number on your crystal or use the "fit" method.

    Forget these charts, they are worthless to anyone doing crystal replacements.

  6. #6
    Registered user. Paris7's Avatar
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    Default Re: Proper Watch Crystal Size (RE: Jon Hanson)

    I'm nearly there with a flat extra thick crystal replacement. It has been in the bezel once but popped out, (it may need a tiny dab of UV glue). However, at the moment I am not getting it to 'snap' back in from the front of the bezel. It's a coin silver Bay State case circa 1884 and has no screw in bezel seat, the seat is an integral part of the(hinged) bezel.

    So, as TomR was asking, could gently heating the bezel help?... is that a possible answer, or is it a total no no?

  7. #7
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    Default Re: Proper Watch Crystal Size (RE: Paris7)

    Paris on some car bearings you actually heat up the in an oven so that the bearing will expand then you drop it on the spindle and the mount becoumes a press fit after it cools. I would think if you put the bezel in the oven at 300'F or so and keep it in the long enough to heat the complete bezel and wear gloves that it would expand enough to allow you to pop the crystal in without any long term damage to the bezel.
    Last edited by 49stude63; 08-11-2009 at 07:47 AM.

  8. #8

    Default Re: Proper Watch Crystal Size (RE: 49stude63)

    As I think I've posted here before somewhere... I use a Paulson bezel warmer to heat bezels to make crystal fitting a bit easier. It also allows you to fit that crystal that will almost - but not quite - snap in. It's easier to us this with screw or snap on crystals, but is possible with the hinged type. You just need to hold the bezel against the warmer with a cloth. As was mentioned earlier, warming in the oven should have the same effect. Just note, you have to work fast. Bezels and cases cool pretty fast once removed from the heat. I snap the crystal in as I am sliding it off the heater.
    Attached Thumbnails Attached Thumbnails BezelWarmer.jpg  

  9. #9

    Default Re: Proper Watch Crystal Size (RE: Scott Erholm)

    Quote Originally Posted by BCMontana View Post
    The crystal itself measures 1.516", and if I cross-reference that to the chart given in the wiki article, that would be a 17 1/16 size. However, the label has sizes 18 5/16 and 17 5/8 on the label! What's the deal?
    It's not out of the question to have mislabeled crystals. I do come across them from time to time. Looks like you found one. You are correct that, according to your caliper reading, this crystal is a 17 1/16.

  10. #10
    Registered user. Paris7's Avatar
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    Default Re: Proper Watch Crystal Size (RE: Dave Coatsworth)

    Great stuff, I'll have a go at heating it, I do remember your post now Dave, I'd forgotten about your Paulson bezel warmer. Rather than buy one and use it once every 10 years I was wondering if a pan of boiling water would do the trick. Whatever method, it might be an idea to take the movement out first of course...

    If you don't hear from me, I'll either be sweeping up the glass or putting the fire out; or possibly both.

  11. #11
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    Default Re: Proper Watch Crystal Size (RE: Paris7)

    I use a 60 watt light bulb to heat bezels, to insert crystals. The shape of bulb lends it self to holding bezels on top of them. Caution the bezel will be very hot when to go to remove it, even after only 10-15 seconds. I take them off with tweeters.

  12. #12
    Registered user. Paris7's Avatar
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    Default Re: Proper Watch Crystal Size (RE: Bill B)

    Quote Originally Posted by Bill B View Post
    I use a 60 watt light bulb to heat bezels, to insert crystals. The shape of bulb lends it self to holding bezels on top of them. Caution the bezel will be very hot when to go to remove it, even after only 10-15 seconds. I take them off with tweeters.
    Great idea for non hinge bezels Bill... but too late for me! I heated mine very briefly in the oven; it worked! Thanks all.

    Bill, talking of "tweeters" our neighbours have been rebuilding here in Paris, and up came their mice. It's been like the Battle of Wounded Knee here, Ghastly poison in every corner, I'm painting X mice on the side of my computer. 5 kills yesterday and another came out, did the tango, and dropped dead while I was trying to fit the crystal into the heated bezel - talk about distractions...
    Last edited by Paris7; 08-11-2009 at 11:47 AM.

  13. #13
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    Default Re: Proper Watch Crystal Size (RE: Paris7)

    You can do hinged bezels the same way, you just hold the case in your hand till you can feel the heat. I really met tweezers, but if you could get a couple of tweeters to behave long enough and cooperate you could use them to replace the crystal. Glad that you got it worked out.
    Last edited by Bill B; 08-11-2009 at 12:01 PM.

  14. #14

    Default Re: Proper Watch Crystal Size (RE: Bill B)

    Quote Originally Posted by Bill B View Post
    I use a 60 watt light bulb to heat bezels, to insert crystals. The shape of bulb lends it self to holding bezels on top of them. Caution the bezel will be very hot when to go to remove it, even after only 10-15 seconds. I take them off with tweeters.
    That is really all my Paulson heater is. There is a 40 watt light bulb inside the housing. And, yes, the bezel gets VERY hot! I slide the bezel off into my left hand, where I'm holding a small towel while simultaneously popping the crystal in with my right hand as I'm sliding the bezel.

  15. #15

    Default Re: Proper Watch Crystal Size mm vs OLD STYLE #'S (RE: Paris7)

    You may have this explination of crystals and their markings already but it's a conversion for most all crystals w/ old markings.
    Attached Thumbnails Attached Thumbnails Sizing-Systems.jpg  

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