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Gasket advice from modders?

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Hi guys (and gals?),
Anyone have a good source for a variety of DECENT caseback O-rings? Every other set seems to be waaay too big with stupid size ranges from tiny to huge (96 pieces, 144 pieces, too thick, too thin). Anyone have luck with a useful set for use in subs and datejusts? Link would be GREAT!!!

Thank you for responses,

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Don't buy into those Chinese packs, your best bet is to pay the more expensive retail prices from cousinsuk, and alike, these are more to gen spec.

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OK guys let's take it a step further this is RWG cc not a noob board for the latest V whatever, we build: nitril or viton gaskets?


My research has led me here:



Re: Which Dive Watches Use Viton Gaskets or Seals?

as an engineer specialized in very high pressure (for the oil drilling industry) I can summarize here advantage and disadvantage of Viton again Nitril

Viton advantages over nitril:
very resistant to chemicals specially oils
very resistant to high temperature (up to +300°C)

disadvantage over nitril :
less flexible material need more precise grooves
subject to break if not corectly handeled
more porous than Nitril

I do not see a that big advantage of viton against nitril for watches , exposure to very high temperature is a non sense for a watch , and we rarely dip a watch in a corrosive athmosphere !

the fact that nitril is more flexible than viton gives a good advantage concerning the necessary torque to wind th watch (manufacturers who use viton are obliged to grease thoses)

so let us say that it is a plus "on paper" but not a real advantage ... a little bit like the helium escape valve on divers
JM "
Anyone think differently?
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"Anyone think differently?"

Nope, I agree.


When someone buys a cheap case back gasket assortment on eBay etc there is no telling what the gaskets are made out of.  Most supply houses carry good quality gaskets (hopefully).


Some gasket info...


Screw down backs:

Case back gaskets are sized by their inside diameter and thickness, both O ring and flat types.  The ID can be obtained from the gasket seat in the case or the lip/groove on the case back but the thickness is sometimes hit or miss.  Measuring a used gasket will not always give an accurate measurement because the old gasket may be compressed to an out of round shape.


You want the gasket to compress fully so that when the back is screwed down the case back seats against the case without squeezing the gasket too much or not sufficiently compressing the gasket...this is where hit or miss and developing a 'feel' for the process comes in.  You do not want the gasket showing from the outside after the case back has been tightened (because the gasket is too thick) but there may be a few exceptions to this.  You also do not want the case back bottoming out before the gasket is compressed and this is sometimes hard to determine. 


When the watch is a replica, vintage, obscure brand, no published specs etc, it takes precise measurement or hit or miss until you determine the correct size.  Always lubricate the gasket with silicone or something similar and be careful not to allow lubricant to get down into the case or on the movement.  Rolex and some other companies use gasket/thread grease (Fomblin, Krytox etc, aka 'high vacuum grease') and it also prevents stainless and titanium threads from galling or seizing.  The catch:  Fomblin is about $80 for 20 grams.

I had a rolex 160xx with the case back seized and when I finally got it apart (penetrating oil/Bergeon 5700 case tool and a LOT of downward pressure), it removed some of the threads on the case back (the back was stuck when I bought it).  A drop of Fomblin etc would have prevented it.


From the Edwards website:

Fomblin® Grease:

This grease is an excellent lubricant for sliding elastomer seals, and exhibits the chemical inertness typical of the Fomblin® range.

It has a very low vapor pressure and is suitable for use in the presence of gaseous and liquid oxygen under severe conditions.

(Edwards specializes in vacuum devices etc)


Krytox GPL 205 is a little bit cheaper, it's what I use.


Snap on backs:

The same rules apply but it is sometimes harder to tell if a flat gasket is too thin or not.  Silicone is fine, no $80 Fomblin needed.  


'Red' plastic (polyurethane) gaskets like used on some snap back omega, Gucci etc.  No lubricant is used.  Gaskets must be an exact fit, sometimes a hassle, easily damaged.

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