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  1. #1
    Registered user. RJSoftware's Avatar
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    Default home made watch crystals...?

    Anyone ever try to make homemade watch crystals..?

    Seems like something could be done to make those hard to find watch crystal sizes.

    Making a form for the plastic to be molded upon doesn't sound too impossible. Especially for round pieces. Maybe something turned on the lathe to fit, maybe wood...

    Seems like there's allot to choose from in the way of plastics materials. I was even thinking of clear plastic liter bottles. Or might be too flimsy weak.

    Ideas, yes no, chuck it out the window...?


    Update: Here is link to youtube video showing how to do homemade vaccum molding.
    http://www.youtube.com/watch?v=eUB58z8apTE
    Last edited by RJSoftware; 08-06-2012 at 10:53 AM.
    [Discovery is about to be destroyed by the birth of a new star]
    HAL 9000: I'm afraid.
    Dave Bowman: Don't be. We'll be together.
    HAL 9000: Where will we be?
    Dave Bowman: Where I am now.

  2. #2
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    Default Re: home made watch crystals...? (RE: RJSoftware)

    My good friend is a glass blower, and I had him make a crystal for me. While he is a very talented and accomplished glass blower, it took him quite some time to do (about 2-3 hours). It does the job, but there are a few bubbles, which is just not suitable for me. So plastic might be the way to make your own, but then you are stuck with the dreaded plastic crystal...

    I do have an industrial vacuum press and numerous plastics though....

  3. #3
    Registered user. RJSoftware's Avatar
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    Default Re: home made watch crystals...? (RE: Phil7153)

    I tell you I have some watches that surprized/shocked me totally that the crystal on them was plastic. What happened was I found a acrylic glass polishing kit. It contains various grades of embeded sand paper that goes really high like 25,000 grain. By the time you use that one the acrylic is shining like brand new. But the kit wont do glass, nothing happens. So I checked out my watches with crudy lenses and was surprized by how many where plastic.

    But the point being I don't think it's that uncommon. I like the vaccum molding process and now it just looks like the problem is finding a supply of clear acrylic the right thickness.

    I suppose that in the vaccume molding process I would have to have excess so to cut off and then later square off with maybe grinding wheel.

    Making the mold would be the hardest part. I guess you have to reduce the diametor of the mold by acrylic thickness X 2. Then maybe add .01 or something for the snap in quality. Or not...!

    How to make square/rectangular crystals. I don't know. Maybe carve wax, but I bet that is difficult. Maybe mold something with clay, test fit with pieces of the acrylic. Maybe first use clay to get the shape, then use that to form some wax, trim the wax for crystal thickness on sides and rub back smooth.... I don't know...
    [Discovery is about to be destroyed by the birth of a new star]
    HAL 9000: I'm afraid.
    Dave Bowman: Don't be. We'll be together.
    HAL 9000: Where will we be?
    Dave Bowman: Where I am now.

  4. #4
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    Default Re: home made watch crystals...? (RE: RJSoftware)

    I read somewhere (probably Chicago School of Watchmaking) a description on how to shape plastic crystals from a flat sheet. If I remember right it involved heat and shaping over some curved "mold".

    I also remember an old TV documentary about a watch maker/collector who demonstrated how he cut a crystal from an old light bulb. Perhaps a bit thin!? It was not the ordinary small bulbs but an oversized of some sort. (It was many years ago and I do not recall if it was for a verge watch or what!)

    Polishing acrylic crystalls is not that hard. One have to use a fins abrassive paper and remove any deeep scratches and then polish back the clearness with e.g. Polywatch.
    I have also tried with CD polishing kits and it seems to do the same job as Polywatch but at a much better prize.

    I recently bough a kit for repairing arylic headlights on cars which also sounds promising but I have not yet gotten round to try it out.

  5. #5
    Registered user. R.G.B.'s Avatar
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    Default Re: home made watch crystals...? (RE: Skutt50)

    I've made a few using dollar store reading glasses for blanks. Shaping with a rotary tool and finishing by hand sanding to get the final shape. From there a quick once over with the acrylic polish.
    Attached Thumbnails Attached Thumbnails hi-res_IMG_946.jpg  
    Rob

  6. #6
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    Default Re: home made watch crystals...? (RE: R.G.B.)

    you know it still surprises me that people are surprised to find plastic or acrylic glasses used in watches, when I started in the trade in the early 70s practically every new watch had acrylic glasses, this includes the Rolexes, Omegas, Longines, Certinas etc, etc, only makers like Patek would use paper thin sapphire crystals in their thin gold cases,

    so that 1972 $1400 Rolex GMT master used an acrylic glass.

    sure it scratches easily, it also polishes out easy too, a quick touch on the buffing wheel with some Crystal Kleer compound took most, bar the deep scratches out.

    the 200 metre dives watches of the day used 3mm thick armoured acrylics, even when they came in every few years for a service with the glass scratched so badly you could hardly see through it and would quite often have cracks in the plastic and yet would still be watertight, the acrylic glass would survive underwater impacts with objects that will break a mineral glass.

    the Japanese started making watches with mineral glasses around about then, then years later most makers followed, and the cost and manufacture of mineral crystals became cheaper and better that even the $5 cheapy has a mineral glass.

    the use of plastic bottles for watch glasses is not a bad idea, although probably a bit thin for open faced watches, way back when wrist watches started to first show up, they would have glass in them, this was the same stuff as used in a window, soda glass, quite brittle, not a real problem in a pocket watch, but a wrist watch, one option was to use celluloid, a watchmaker would buy flat sheets, use a tool to cut a circle out of the sheet, this tool would cut a bevelled edge in the thin sheet, the idea was to cut the circle oversized, the Robur Glass tool was made to fit these glasses, the cup and dome dies would curve the flat circle and spring fit it in the bezel, the only real downside of celluloid it would go yellow after a while.


    making a square glass, well one way is to take a flat metal block, drill a small hole in the centre, fit a short bit of tube so a hand air pump like a very large syringe or dust blower can be attached, a piece of the acrylic is placed on top, this needs to be 2-3 times the size the finished glass, make a die out out of 1 or 2mm sheet brass or aluminium to the size of the bezel fitting and clamp that over the acrylic, warm the whole lot in an oven until the acrylic is soft, then with the air pump puff the acrylic up to dome or curve it and hold that until it cools, then you only have to cut out and file it up to fit.

    rectangular curved cases like in post #5, find something that matches the curve, warm a strip of acrylic and bend it around the former and let it cool.

    the stuff I use is Shinkolite, made by Mitsubishi Rayon, easy to form, takes a great polish, thickness from 1mm
    http://www.mrc.co.jp/shinkolite/technical-info/index.html

  7. #7

    Default Re: home made watch crystals...? (RE: dAz57)

    I made one out of a cassette tape case, it was an octagon shape, 12 size. All of watch people I showed it to were impressed.

  8. #8
    Registered user. R.G.B.'s Avatar
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    Default Re: home made watch crystals...? (RE: NC Plumber)

    Thanks for the Shinkolite link dA. Worth looking into.
    Rob

  9. #9
    Registered user. John A's Avatar
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    Default Re: home made watch crystals...? (RE: R.G.B.)

    I am having a problem finding a crystal for my Certina. Has anyone tried casting with epoxy resin?
    I have the original in reasonable shape except fine cracks so should be easy to make a mould with casting rubber
    any ideas?Click image for larger version. 

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  10. #10
    Registered user. R.G.B.'s Avatar
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    Default Re: home made watch crystals...? (RE: John A)

    I've never tried epoxy for forming and it might be problematic with the mix being cool or hot. Being too brittle or soft would be the result. An alternative might be to fill the cracks with cyanoacrylate and then sanding and polishing.

    Rob
    Rob

  11. #11
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    Default Re: home made watch crystals...? (RE: John A)

    Quote Originally Posted by John A View Post
    I am having a problem finding a crystal for my Certina. Has anyone tried casting with epoxy resin?
    I have the original in reasonable shape except fine cracks so should be easy to make a mould with casting rubber
    any ideas?Click image for larger version. 

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ID:	150672
    did you look here? http://www.ofrei.com/page_164.html

  12. #12

    Default Re: home made watch crystals...? (RE: dAz57)

    I once tried useing RGB's method of making a watch crystal,but with no luck...the i couldn't get the glass thin enough, and it was taking forever...using a Casette holder might be a good idea, since it is the right thickness....the only trouble now is finding a old one that wouldn't be all beat up,worse then the crystal you are replacing.....anybody try just using crystal blanks

  13. #13
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    Default Re: home made watch crystals...? (RE: davestanda)

    Quote Originally Posted by davestanda View Post
    I once tried useing RGB's method of making a watch crystal,but with no luck...the i couldn't get the glass thin enough, and it was taking forever...using a Casette holder might be a good idea, since it is the right thickness....the only trouble now is finding a old one that wouldn't be all beat up,worse then the crystal you are replacing.....anybody try just using crystal blanks
    watch plexis or glasses are made from Acrylic Resin, this can be machined, filed and polished to a high luster and is crystal clear, some plastics which are moulded for components don't polish well.

    you can buy shaped blanks already curved to suit, you could get one close to size that will only need a bit of filing to fit it.

    the style of plexi on this one appears to be a cylinder style, that is a curved top with flat sides, might have different names elsewhere.

    otherwise make your own from Shrinkolite sheet, can be heated and moulded, http://www.mrc.co.jp/shinkolite/tech...nfo/index.html

  14. #14
    Registered User doug sinclair's Avatar
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    Default Re: home made watch crystals...? (RE: dAz57)

    My late father was a Depression era watchmaker. This was a time when there were no fax machines, Internet, UPS, no on line catalogs, and sparse supplies of what a watchmaker would need. He showed me about 50 plus years ago how watchmakers would take a square piece of zinc sheet about 3" by 3", turn the corners down, contour the curvature of the sheet to match the profile of the bezel, then saw a hole in the zinc to match the shape of the recess for the crystal. Place a glass crystal that was too large over the hole, the slowly and uniformly heat the glass crystal until it reached the flow point (not the melt point), and a nicely formed crystal that required only a bit of finishing would drop through the hole in the zinc to the bench top, I had watched him do it, but i've never tried it.

  15. #15
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    Default Re: home made watch crystals...? (RE: doug sinclair)

    what was the material, glass or plastic, around that period celluloid was a common watch glass.

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