Where can I get such a crystal?

[Delgetti]

I'm working on a 7734 chrono and the crystal has some very deep scratches. Polishing doesn't really work so I would like to replace it. But I dont know where to look on the cousins webpage. The crystal wears a ring with a tachymetre scale on the inner diameter. The wall seems to be absolutly cylindric not conic. Outer diameter is aprox. 33.2 mm, inner is aprox. 31.3 mm, height 4 mm. Any ideas?

[Latvas]

I'm working on a 7734 chrono and the crystal has some very deep scratches. Polishing doesn't really work so I would like to replace it. But I dont know where to look on the cousins webpage. The crystal wears a ring with a tachymetre scale on the inner diameter. The wall seems to be absolutly cylindric not conic. Outer diameter is aprox. 33.2 mm, inner is aprox. 31.3 mm, height 4 mm. Any ideas?

Ebay


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[rogart63]

Try tiptopcrystal. com . Actually done that a year ago and maybe still have one left. Have a look. Think it was divertite i used. 

Edited January 1, 2019 by rogart63

[rogart63]

Inner diameter is slightly larger then 31.1. But i glued the inner ring with a small dap of crystal glue. Hasn't come of yet . This one i had was 33,3 but i used the 33,2 already. BTW it was a evertite . And it's 4 mm high on the spot. 

[rodabod]

Maybe a Sternkreuz ATCH? Take a look at their data sheets.

[Delgetti]

Thank you. Evr tite looks very good, but it seems it's only available in the US?

I think I will try the ATCH as I have a cousins order anyway. If this one doesn't fit I will go for the evr tite.

[rogart63]

4 hours ago, Delgetti said:

Thank you. Evr tite looks very good, but it seems it's only available in the US?

I think I will try the ATCH as I have a cousins order anyway. If this one doesn't fit I will go for the evr tite.

If you want i can send you mine. Think a 33,3 could work? I have a the envelope for the 33,2 but it has fallen out. Maybe it's here somewhere . Or in an other envelope. 

[nickelsilver]

For these old chronos with a printed ring as tension ring and no parts available, I often use a "generic" (quotes because randomly enough a few Omega crystals have fit the bill in the past) armored crystal which I modify. As luck would have it the usual tension ring for a given outside diameter is often smaller than the printed ring. I make a friction chuck out of plastic in the lathe that will just allow the crystal to snap into, backwards, then turn the inside to fit the original ring. Takes about 15 mins start to finish if you are accustomed to latge work.

[rogart63]

29 minutes ago, nickelsilver said:

For these old chronos with a printed ring as tension ring and no parts available, I often use a "generic" (quotes because randomly enough a few Omega crystals have fit the bill in the past) armored crystal which I modify. As luck would have it the usual tension ring for a given outside diameter is often smaller than the printed ring. I make a friction chuck out of plastic in the lathe that will just allow the crystal to snap into, backwards, then turn the inside to fit the original ring. Takes about 15 mins start to finish if you are accustomed to latge work.

Interesting. Can you show us how you do that? 

[nickelsilver]

16 hours ago, rogart63 said:

Interesting. Can you show us how you do that? 

I usually have some PVC or Delrin barstock around, which is useful for many things including oddball supports and pushers for case work, making movement holders etc. I'll chuck up a scrap of suitable size and bore out a recess to accept the crystal. You have to creep up on the final diameter so the crystal fits in snugly but not too tight (and not too loose!). There's always a hole in the center to allow pushing the crystal out when finished. Once the crystal is in it will be running very true as you leave the plastic in after turning the recess- this means you can do accurate work even with a wonky chuck. Now, with a very sharp tool, bore the crystal to just fit the ring.

The pics show a tension ring crystal I had lying around, I hope they're illustrative enough.

 

[rodabod]

That is excellent. Thanks.

[rogart63]

Great work. Thanks for sharing.