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Discussion Starter #1
I've just stripped a dozen or more 6309s and SKXs and it got me to thinking which is the best crystal retaining system.

Personally I would be inclined to think the nylon gasket in good condition would be better than the 6309 retaining ring system, what do the experts think ?
 

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Well I'm no expert, but my experience with retaining ring crystals is that they leave a little to be desired for true water resistance. You need just the right "pop" on the crystal press.

I also find the nylon gasket must be new. Never re-use it with the replacement crystal. Nice you readjust by inserting one side down farther if needed.

I'd love to hear the deepest dive rating quoted by Seiko on a retaining ring system.
 

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Discussion Starter #4
IMO (and I'm no expert) the best crystal sealing system is the one used in the Citizen Ecozilla: a nylon O-ring that goes around the crystal perimeter coupled by a threaded crystal retainer, which makes the watch suited for mixed-gas diving without the need of a He valve.

Look at Duncan's post: http://www.thewatchsite.com/21-japanese-watch-discussion-forum/126130-ecozilla-mr-galbraith.html#post1008466
Like you Chris i am no expert but I would imagine the screw down ring takes some beating and I wouldent even compare it with the two methods I mention at the start of this post, chalk and cheese :)
 

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I am surprised the 6309 diver retaining ring method and 7002 diver friction fit nylon gasket type actually work when it comes to diving. They are a bugger when using after market crystals, gaskets or retaining rings as they need to be a precise fit and rarely are.
Although they are an arse to unscrew I favour the screw down style of the 7c43. I just feel more confident with the method.
However am I too heavy handed for delicate watch repair so very much to blame for all the ones I got wrong. :undecided:
 

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IMO the L-gasket + retainer ring is still the best method. That's why Seiko uses it for the 300m and 1000m Pro Diver series.
 

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I am not totally sure John, but I don't think that my 300m Sub even has a screw down retainer. Clip on I reckon? Which does surprise me as I've always thought screw down was the business.
 

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With the L shaped gasket would the water pressure help by pressing the crystal into the gasket and therefore helping it to seal ?
I believe that is the idea, John. The L-gasket is self-tightening as external pressure increases.
 

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Yeah, but the reason Seiko chose this geometry of the crystal gasket is not to increase the water tightness sealing, but to allow the He gas that penetrates the watch during saturation diving to escape it without causing harm due to built in internal pressure and at the same time dismissing the necessity of a He valve a la Omega Seamasters (2nd external crown) or Rolex Sea Dwellers (automatic inbuilt valve).

The question begs to be asked: having said the above, what about Citizen's Ecozilla solution to the He gas penetration, which does not employ a He valve nor a special L-gasket, and still allows the watch to be taken down to saturation diving all the same.

How does the Ecozilla deals with the He penetration matter? On another thread, Duncan guesses that the crystal retaining ring on the Ecozilla, which is threaded, is the sole responsible to maintain "everything inside" upon dealing with the inbuilt pressure from the He, and that it is not enough force to push out on the crystal through the threaded ring nor make the watch explode.

Provided this all works on the field to a T, then Citizen can teach a thing or two to other companies about how to make a no B.S. sat dive watch. He valve who? L-shaped gasket what? Yeah right!

Just to add more ??? to the question, the ecozilla's big brother (the autozilla) have the same threaded crystal ring but at the same time employs an automatic He valve at the 10 o'clock position. Maybe an overengineering kinda thing or just to be extra safe? Maybe plain overkill to me, since the company has rated the younger brother a professional saturation diver all the same.
 

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Yeah, but the reason Seiko chose this geometry of the crystal gasket is not to increase the water tightness sealing, but to allow the He gas that penetrates the watch during saturation diving to escape it without causing harm due to built in internal pressure and at the same time dismissing the necessity of a He valve a la Omega Seamasters (2nd external crown) or Rolex Sea Dwellers (automatic inbuilt valve).
Hi Chris,
I believe the L-gaskets do not allow free passage of the smaller helium molecules, but rather prevent them from entering (or more accurately let them enter much more slowly). See the words of Tokunaga-san himself, here.
 

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Hi Chris,
I believe the L-gaskets do not allow free passage of the smaller helium molecules, but rather prevent them from entering (or more accurately let them enter much more slowly). See the words of Tokunaga-san himself, here.
Very true, and if I'm reading the Seiko graph correctly - a Helium gas dive profile at 300m for two and a half days gave internal overpressures of 60 psi, 48 psi and 33 psi in the non Seiko Professional watches.
In comparison the Seiko Professional 600/1000m divers only reached about 8.5psi internal pressure.
I think this is a real testament to the simple but very ingenious design of the Seiko low Helium permeability "L" gasket system.
To give a real world comparison, the strongest champagne bottles can withstand 70-90psi - so no wonder that watch crystals were popping like champagne corks!
It would be very useful if one of our Japanese reading members could fully translate the information on the graph.
 

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re

As mentioned above the screwed down retaining ring is SUPERIOR to the standard nylon gasket fit and pressed on retaining ring!

Nylon gasket fits are oks BUT one SHARP knock and the glass can often pop reet out of the case, HAVE done this a few times with TAGs when centre punching a second ratchet hole. :)
 

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Also with the screwed retaining ring to achieve FULL depth rating you really need the thin retaining ring nylon packer, as I've WET tested TUNAs to 375 Metres (125%)depth with the L gasket just beginning to show signs of water entry! :undecided:
 

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Also with the screwed retaining ring to achieve FULL depth rating you really need the thin retaining ring nylon packer, as I've WET tested TUNAs to 375 Metres (125%)depth with the L gasket just beginning to show signs of water entry! :undecided:
That's interesting. I thought the plastic ring was to protect the glass crystal when tightening the crystal fixing ring. I figured it was made from PTFE. I had no idea it had anything to do with sealing.

Myles
 

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That's interesting. I thought the plastic ring was to protect the glass crystal when tightening the crystal fixing ring. I figured it was made from PTFE. I had no idea it had anything to do with sealing.

Myles

I agree.

To the best of my knowledge, the nylon ring function is to help distribute the pressure from the threaded retaining ring over the crystal and also for preventing it from cracking or break upon screwing it down. Not sure if it has anything with enhancing the sealing system through the crystal.

Besides that, other professional diver's watches - such as the Ecozilla - that employs the threaded retaining ring system do not use a nylon/plastic ring ensandwiched between the crystal and the ring, and these watches are thoroughly sealed without such nylon ring.

Maybe the tunas (that hadn't the nylon ring installed) that were prone to failing in the water testing had their L-gaskets in bad shape?
 

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Hi Chris, I don't know first hand about the watch - not being lucky enough to own one, but I think the truth may be that, like you said, the nylon or teflon fixing ring gasket is there to distribute the load AND to allow it to turn more easily against the crystal.
I think, from looking at the cross sectional case drawing of the 1000m diver, that the glass fixing ring not only holds the crystal in the case against internal overpressure - but also doubles up to increase the sealing capability of the L gasket.
If you look at the drawing, the lower part of the threaded ring actually bears against the L gasket - which would therefore compress the gasket and push it sideways between crystal and case.
I think you did the battery change tutorial on the Golden tuna, so you've seen the parts first hand, so maybe you can comment on my thoughts?
Apologies for the bad drawing - I'll try to find another.
EDIT - whilst looking for a better drawing, I found a post from WUS which appears to confirm my thoughts - and a lot more eloquently explained too.
So the crystal ring forms an integral part of the seal - and the case shouldn't be pressure tested without it being fitted.
http://forums.watchuseek.com/f77/exploded-view-605936.html#post4450220
 

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Hi Chris, I don't know first hand about the watch - not being lucky enough to own one, but I think the truth may be that, like you said, the nylon or teflon fixing ring gasket is there to distribute the load AND to allow it to turn more easily against the crystal.
I think, from looking at the cross sectional case drawing of the 1000m diver, that the glass fixing ring not only holds the crystal in the case against internal overpressure - but also doubles up to increase the sealing capability of the L gasket.
If you look at the drawing, the lower part of the threaded ring actually bears against the L gasket - which would therefore compress the gasket and push it sideways between crystal and case.
I think you did the battery change tutorial on the Golden tuna, so you've seen the parts first hand, so maybe you can comment on my thoughts?
Apologies for the bad drawing - I'll try to find another.
EDIT - whilst looking for a better drawing, I found a post from WUS which appears to confirm my thoughts - and a lot more eloquently explained too.
So the crystal ring forms an integral part of the seal - and the case shouldn't be pressure tested without it being fitted.
http://forums.watchuseek.com/f77/exploded-view-605936.html#post4450220
Yes, but the sole function of sealing the crystal against water penetration is shouldered exclusively by the rubber L-gasket. Any increases in protection, or extra protection against water intrusion via the teflon ring is always welcomed, but the watch should remain water tight even without it, 'cause sealing through the crystal happens via the L-shaped rubber gasket being squeezed by the pressure applied by the threaded retaining ring. The abscence of a teflon ring should only increase the risk of cracking the crystal upon tightening it down, at the most.
 

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Yes, but the sole function of sealing the crystal against water penetration is shouldered exclusively by the rubber L-gasket. Any increases in protection, or extra protection against water intrusion via the teflon ring is always welcomed, but the watch should remain water tight even without it, 'cause sealing through the crystal happens via the L-shaped rubber gasket being squeezed by the pressure applied by the threaded retaining ring. The abscence of a teflon ring should only increase the risk of cracking the crystal upon tightening it down, at the most.
All true - but as I said in my post "the nylon or teflon fixing ring gasket is there to distribute the load AND to allow it to turn more easily against the crystal."
I didn't say or infer that it's an extra seal.
 
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