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Mlgboy

Replacement domed acrylic crstal

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Hi All, looking for some help identifying the correct crystal type for a Tudor Advisor Alarm ref 7926 circa 1958. The watch has a retaining bezel over the crystal which is .5mm thick with an outer non stepped diameter of 29.4mm. Overall height is 3.7mm. Any help would be much appreciated.

Mark

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On 9/15/2019 at 2:34 PM, jdm said:

These are called top glasses.

https://www.cousinsuk.com/product/domed-top-sternkreuz-st

They may need a slight sanding to fit. Download and check the catalog.

Found the correct inside diameter at 28.4 with an outside diameter of 29.7 and actually need 29.4. Any recommendations for reducing the size accurately while leaving a clean finish?

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    • Yes I hijacked this thread, did not mean to , sorry sorry.  
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    • Hi Nickelsilver, Thank you for all the help.  Will search for the tech sheet. I have many used genuine hairsprings and balances that I have been vibrating together. Need to place order for more hairsprings of compatible springness.  Been trying to experimentally find a compatible HS of known CGS.   Strength is proportional to area of the coil outer circle. I think I may find CGS direct out of this tables.  Will keep you posted.  Thank you, great help.   Best      
    • Found one of the tables, it's in French but easy to figure out.   If doing the test spring process, the formula is K=K' (D/D') 2 K is the CGS number you're looking for K' is the CGS of the spring you test D is the diameter of spring you need, at the pinning point D' is the diameter of the correctly vibrated test spring at the pinning point.   Sorry to the OP Joe and I are hijacking the thread a bit, maybe a mod could move it to a new thread?    
    • Thank you all for your kind welcomes.
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