Can’t Find a Crystal

[cgelbard]

Hi everyone, I’m having some trouble locating a crystal for a watch I’m working on. I’ve looked through the GS & BB catalogs, but can’t find the correct one, or anything that’s even that close. It’s a Girard Perregaux men’s watch circa 1945. According to my caliper, the crystal measures approx. 22mm x 18.3mm, it has a lengthwise curve and a flat width. I find it curious that I’m having difficulty locating a crystal as I don’t believe this watch is particularly rare or exotic. Any suggestions as to what I should do? What do you do when you can’t find the correct crystal for a watch?

Appreciate any help or guidance!
-C

[namonllor1953]

Go to these two links and I’m sure you’ll figure it out.
When you download the course you’ll want to look at lesson 3

http://www.rwgforum.net/topic/157892-chicago-school-of-watchmaking-courses-e-book-uploaded-and-shared/

and here’s a link to the crystals

http://www.ebay.com/itm/BB-Glass-Watch-Crystal-CX-Cylinder-Rectangle-Sharp-Corner-Shape-NOS-Select-Size-/271720764633

Sure hopes this helps…

[chris mabbott]

I’m not 1000% sure of this but I seem to remember reading…..somewhere, that due to the vast array of “fancy shape” special crystals that were needed, that most jobber manufacturers sold them in various “close” sizes, and that the watchmaker would grind them down to fit a particular watch.

I don’t remember where I read that because I don’t collect wrist watches and it was something I stumbled upon while also looking for a crystal.. But it is an option if you use care and a diamond stone as the type you’re working on are thick, square and small..

Watch this video Crystal Grinder

[stevefitzwater]

Yeah, I have 5 watches that need similar crystals, so please update us on what you find..

Thanks..

[randy]

All good info from the gent’s above, and Chris is correct about crystals coming in sizes that are “close” to the finished dimensions.
Open your G-S catalog, and I think this is a CMX type. Start there, and just take the crystal and lay it over the one that appears to be the closest match. The pics in the catalog are pretty close to the true dimensions. That may get you to one that may not read the same size as you’ve measured…but to one that should be close enough to grind back to fit.
If it’s plastic..that’s easy. If it’s glass you chose,..then either a diamond grinding wheel…or I have had good luck using different grades of diamond files.

Good luck !

[chris mabbott]

Randy, have you ever tried those diamond grinding bench plates that are sold on ePay? I see them all the time and the price is half of the ones sold on Cousins UK..

I was wondering if there is a quality difference/issue….made in India, or something?

[david pierce]

Chris,
This probably won’t do you any good in Spain but Harbor Freight in the U.S.A. sells a set of 3 diamond plates for less than $10.00. As far as I know they are made in China. There are other materials that will cut glass and this might be a good use for the green silicon carbide grinding wheels that I have found to be next to worthless grinding metal.
david

[chris mabbott]

Do you think those green wheels would work on glass David? I was wondering what the wet wheel was that is used on the vid link I posted above?

For that price they might be worth me going the harbor freight way, I wouldnt get nailed by the import tax then..

[randy]

I haven’t tried them Chris…but I’m going to go search for them now !

[cgelbard]

Hi all,

First of all thanks everyone for all the great info . Yes it’s a CMX type crystal, should have mentioned that in the original post. I’m aware that many crystals were cut close and then adjusted to fit, but with this darn crystal I hadn’t been able to find anything that I consider a close enough match. I know how to adjust length or width, but everything I find has either the wrong thickness of material or an incorrect curvature. Also, the original is glass which makes things slightly more difficult, but I think switching to a plastic one might be an option at this point.

So I found three good options

Option #1 – Firstly my go to resources for crystals are the GS & BB catalogs, but I suppose I really should have checked Otto Frei because I found this: http://www.ofrei.com/page1415.html They mainly have 1mm thick blanks online, and I need a 2mm blank, but I’m going to call them on Monday to see if they have them; I’ll be surprised if they don’t. If they do, I can get a 22mm x 20mm blank and then only have to trim the width. They have many different radii, so I’m sure I can find the right curvature assuming they have the correct thickness.

Option #2 – The closest in the GS catalog I can come I believe is CMX 343-2, a Benrus crystal. It’s clearly thicker than what I have, but I think it might be acceptable after trimming the length and width (the thickness of what I have is closest to CMX 334-29F BUT that one also has a curve along the width which mine doesn’t).

Option #3 – Also, I found this site: http://www.crystalfit.com – does anyone have any experience with them? I really hate farming out work but I’m still considering it.

And by the way, if the green wheels are indeed silicon carbide then they should have no trouble with glass.

-C

[randy]

C,
I’ve dealt with Daniel at Crystalfit many times
Nice man…very helpful.
I haven’t sent work to him..but I also haven’t heard anything bad about his services.

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