Dial side watertight?

[Imran]

On an oyster style case, the back is screwed in with an o-ring in place, however on the dial side the crystal appears to be pressed into place. Is there more to it than that, or are the tolerance levels so precise that the pressure fitting of the crystal is enough to make the case watertight. Furthermore, does the bezel play any role, or would the case integrity remain constant even with the bezel off. In Jocke's day date conversion pictorial, one of the shots showed the crystal and bezel fit together and crystal having to be pushed out....wondering how it all stays together and watertight. Would really appreciate some insight on this.
Regards,
Imran.

[joe100]

There is a gasket between the crystal and case. They're pretty stout

[padi56]

Originally Posted by Imran

On an oyster style case, the back is screwed in with an o-ring in place, however on the dial side the crystal appears to be pressed into place. Is there more to it than that, or are the tolerance levels so precise that the pressure fitting of the crystal is enough to make the case watertight. Furthermore, does the bezel play any role, or would the case integrity remain constant even with the bezel off. In Jocke's day date conversion pictorial, one of the shots showed the crystal and bezel fit together and crystal having to be pushed out....wondering how it all stays together and watertight. Would really appreciate some insight on this.
Regards,
Imran.

Today they use a Delrin or Copolymer Acetal gaskets its a highly versatile engineering polymer that bridges the gap between metals watch crystals and ordinary type plastics.Delrin Acetal has great mechanical strength, stiffness and toughness.Delrin also has high impact strength and maintains very good dimensional stability with low water absorption. It is used in many static and dynamic industrial applications.It often replaces the usual materials like Steel, Brass, Bronze, Cooper and Aluminium gaskets or washers.Delrin Acetal have greatly improved the 'part life' because of better wear when used as shims or gaskets and last well and are replaced as part of normal service.

[Andad]

And Delrin is used for the 'brake' in the Omega Speedmaster (on the non-see through caseback models).
Omega didn't want Omega WIS to see 'plastic' bits in their movements.
Even if it was more efficient.

[gregdolley]

I always wondered about this too. When I take off a bezel I notice there seems to be something fused to the underside of the crystal but it kind of looks like part of the crystal too. It's like a thick acrylic ring that's perfectly flush with the outer edge of the crystal. I was never able to figure out whether this part was actually part of the crystal itself, or something separate. Is this the Delrin or Copolymer Acetal gasket?

[Brushpup]

Originally Posted by gregdolley

I always wondered about this too. When I take off a bezel I notice there seems to be something fused to the underside of the crystal but it kind of looks like part of the crystal too. It's like a thick acrylic ring that's perfectly flush with the outer edge of the crystal. I was never able to figure out whether this part was actually part of the crystal itself, or something separate. Is this the Delrin or Copolymer Acetal gasket?

Do you just like to take off bezels for fun?

[Imran]

Thank you all for sharing the knowledge...
Got the info I was looking for, much appreciated.
Regards, Imran.

[Imran]

I had always imagined that perhaps the crystal had a circular protuding lip on its lower edge(wider than the visible width)which would push up against the inside of the case...so that the watch head would be assembled crystal, then movement and finally the case back holding holding both in place real snug. Wonder if such a system is ever used in watch cases.