Are Omega's Dive watches water resistant when the crown is opened?

Archer · Jul 31, 2022

M matlt
Here’s some basics. https://www.ralstoninst.com/news/story/high-pressure-connection-seals-explained
Most/all of my experience is with this type of application. Technically, the flare is what creates the seal, with the threads ensuring proper mating. But there’s no sealant or gasket of any kind.

This is so out of the realm of what is on a watch, it seems fairly silly to suggest this can be done on a watch case mate. As you say, the threads are not what does the sealing on these examples either.

Archer · Jul 31, 2022

P Pkohli
@Archer

May be a silly question for my first post but if Omega screw down crowns are water resistant even when pulled out to the furthest positions, does this also mean it is humidity/moisture resistant? Obviously humidity is a form of water but not sure which is easier to get past the gaskets if the crown is popped out to the furthest position. Assume new seals, gaskets.

Water molecules are water molecules...

Dan S · Jul 31, 2022

P Pkohli
@Archer

May be a silly question for my first post but if Omega screw down crowns are water resistant even when pulled out to the furthest positions, does this also mean it is humidity/moisture resistant? Obviously humidity is a form of water but not sure which is easier to get past the gaskets if the crown is popped out to the furthest position. Assume new seals, gaskets.

@pkholi, for me the salient point is that while the case retains some water resistance with the crown pulled out, it's still best to screw it down. So unless it's really necessary, there's no reason to leave the crown out, or to pull it out under conditions where it will encounter moisture. For example, I wouldn't deliberately choose to set the time while standing in the rain.

Archer · Jul 31, 2022

D Duckie
Looking at the Rolex Twinlock in isolation which we touched on earlier in the thread. It appears as though the screw down component of the design is crucial to the water resistance capability because of the gasket/seal that gets screwed down onto the very end of the Crown tube👎
Without that element of crush on the seal by screwing the Winding crown down onto it. It may not necessary be as effective at keeping the water out as one would imagine🙁
Noteably, the early Twinlocks on the legendary Submariners were routinely swapped at a Rolex service back in the day, for a Triplock as a standard upgrade after the Triplock was introduced.
This probably indicates that the Twinlock had design limitations which were insurmountable. They still rate it for 100 metres though👍

Rolex's choice to use external threads on the case tube is what necessitates them using all the extra O-rings that they need in their various crown designs. Omega uses an internal thread on the case tube, which does a few things...

1 - It keeps dirt and debris out of the case tube and crown threads, because they are never exposed in normal use.

2 - It allows the seal to be on the outside diameter of the case tube. This means that unless you pull hard enough to yank the stem right out of the movement, water never enters the crown system, unlike when you unscrew a Rolex crown, and water can be trapped in the crown and potentially get pushed inside the case when you screw it back down.

3 - It maintains the rigidity of the crown via the case tube. In the Rolex design, when the crown is unscrewed it is not supported by much as it becomes disconnected from the case tube OD. It's primarily the stem and the seals inside the case tube that act on the post of the crown, and you can wobble the crown around pretty easily. This means if it's not screwed down and is subject to a side load, it can allow water in through the deflection that is allowed. On the Omega system it is much more rigid, as the case tube provides the stability to the system, since the crown never loses contact with it.

Why on earth Rolex has stuck with this overly complex and inferior design is beyond me, but likely because they have marketed it to people as the next thing since sliced bread, and they would look pretty stupid changing to something different after all these years of saying it was so great.

Omega crowns use 1 O-ring, because that's all you really need to do the job properly.

Cheers, Al

Dan S · Jul 31, 2022

Archer
Omega crowns use 1 O-ring, because that's all you really need to do the job properly.

I googled, but couldn't find a schematic for a Omega screwdown crown, except the Ploprof, which seems unique. I'm wondering if when the crown is screwed down, it compresses the o-ring against a surface, improving the seal. Or does the o-ring seal the same way on the outside of the tube regardless of the position of the crown?

Archer · Jul 31, 2022

Dan S
I googled, but couldn't find a schematic for a Omega screwdown crown, except the Ploprof, which seems unique. I'm wondering if when the crown is screwed down, it compresses the o-ring against a surface, improving the seal. Or does the o-ring seal the same way on the outside of the tube regardless of the position of the crown?

The only compression is the fit of the O-ring to the outside of the case tube - that doesn't change when it's screwed down.

Dan S · Jul 31, 2022

Thanks, Al, that's interesting.

For those who might be interested, this is the schematic I found for the Ploprof, which is obviously very different. Instead of turning the crown, one turns a threaded ring that pulls the crown inwards. From the schematic, it appears to me that the o-ring is compressed against the bottom surface when the crown is drawn fully inward, and I'm guessing that's what is meant by double sealing/waterproofing. I'm inferring that since the crown is not rotating as it compresses the o-ring, it avoids shearing the rubber.

Screen Shot 2022-07-31 at 10.32.49 AM.png

Duckie · Jul 31, 2022

Archer
Rolex's choice to use external threads on the case tube is what necessitates them using all the extra O-rings that they need in their various crown designs. Omega uses an internal thread on the case tube, which does a few things...

1 - It keeps dirt and debris out of the case tube and crown threads, because they are never exposed in normal use.

2 - It allows the seal to be on the outside diameter of the case tube. This means that unless you pull hard enough to yank the stem right out of the movement, water never enters the crown system, unlike when you unscrew a Rolex crown, and water can be trapped in the crown and potentially get pushed inside the case when you screw it back down.

3 - It maintains the rigidity of the crown via the case tube. In the Rolex design, when the crown is unscrewed it is not supported by much as it becomes disconnected from the case tube OD. It's primarily the stem and the seals inside the case tube that act on the post of the crown, and you can wobble the crown around pretty easily. This means if it's not screwed down and is subject to a side load, it can allow water in through the deflection that is allowed. On the Omega system it is much more rigid, as the case tube provides the stability to the system, since the crown never loses contact with it.

Why on earth Rolex has stuck with this overly complex and inferior design is beyond me, but likely because they have marketed it to people as the next thing since sliced bread, and they would look pretty stupid changing to something different after all these years of saying it was so great.

Omega crowns use 1 O-ring, because that's all you really need to do the job properly.

Cheers, Al

Thanks for taking the time to respond with such detail Al👍

You have brought some great clarity to the different aproaches taken by the manufacturers and confirmed my own observations from what I can glean through limited hands on experience and from what I've seen on the interwebs.

Your point 2 was interesting as it validated my observations around the Triplock where I always considered it to potentially hydraulic water past the internal o-rings if enough was trapped between the inner and outer o-rings when the Winding crown was screwed down👍

Duckie · Jul 31, 2022

P Pkohli
@Archer

May be a silly question for my first post but if Omega screw down crowns are water resistant even when pulled out to the furthest positions, does this also mean it is humidity/moisture resistant? Obviously humidity is a form of water but not sure which is easier to get past the gaskets if the crown is popped out to the furthest position. Assume new seals, gaskets.

Welcome to the forum👍
I know you are asking Al, but I imagine the difference between water tightness and the humidity in the air would be virtually impossible to quantify in the real world, if as you say the seals are in a sound condition.
It's also to be expected that there will be a certain amount of humidity(ambient) present inside the watch from when it's buttoned up at the factory or after service. It's the tolerance level of moisture inside the watch that becomes important.
This is usually evident by foging inside the crystal when the dew point is reached due to temperature changes.
How long the foging remains visible and the extent of the foging determines whether further investigation is required. But seals in serviceable condition should negate any issue👎

Perhaps Al can offer to shed more light?

Are Omega's Dive watches water resistant when the crown is opened?

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Dan S

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