After years of saving up, I got myself a brand new Seamaster Professional Diver 300M (Cal. 8800, the 2018 model in blue and stainless steel). I'd like to take the best care of it while also wearing it every day.

I always tighten down my Helium valve and never touch it (also on the rare occasions I'd have hand my watch to someone, I always tell them not to play with the HE valve or the crown: the bezel is fair play unless they try to force it clockwise). However, I'm not sure what kind of gasket I can imagine the crown has: is it a single gasket inside the crown, or how can I visualize the inner workings of the crown situation inside the 300M?

I feel three "levels" of resistances while screwing it down:
1) I start by rotating the crown backwards to the left while gently pushing so that it catches on the thread, then I rotate it to the right (this allows around ~3 full turns of the crown) and while doing so, I feel the same resistance as if I was winding the watch, in fact I can hear the movement winding, which was the same with my 1120-based SMP as well
2) After step 1 (and around 3 turns) I feel a different kind of faint resistance, which I can only assume some kind of seal making contact with the crown tube. From this point, I can rotate the crown around 45 degrees (or a quarter turn) forwards. If I try to tighten or loosen it at this point, the loosening takes much less force than trying to tighten it further
3) If I tigthen it further than the quarter turn, it reaches a point where I cannot tighten it further, and in fact, I rather turn it backwards to tightness "2" instead to not damage anything

I'd like to know which level of tightness is the best: Halfway between that critical quarter turn? Before?
Is there a way to permanently damage the crown seals of this watch by tightening it too much?
I'm trying to avoid operating the crown as much as possible in general (to avoid having to stress the movement and crown with setting or winding) but I'm kind of terrified of the idea of doing something wrong on the occasions I have to.

Could someone give pointers about this issue, maybe a cross-section drawing of how to imagine this on this model?
Any help is appreciated!
(Photo is for illustration or thumbnail reasons only)

 

Here's some good advice:



https://omegaforums.net/threads/screw-in-crown-design-new-seamasters.24461/#post-270819

 

Thanks! I'm wondering and really hoping if the 300M has this same crown system (as they say "600M" on the images assuming its a Planet Ocean), someone also wondered in the comments but it was left unanswered. It'd be good to have a 5ATM safety even with a fully open crown, but somehow I don't trust that claim from the image (as it's not from this model and not from Omega directly)

Anyways, I'll probably take it to an experienced watchmaker in town and ask them to tighten to a point where they would on other watches, just for reference and take a picture of the crown position and how tight/loose they get it

 

A long explanation but, imho, an easy answer.

My father was one of those people who was good at everything. He died some years ago - he was an officer in the British Army through the Second World War. I’m 69 and I miss him every day. But he taught me everything.
So … don’t force it (I can hear his words). Tighten it until you can feel it’s sealed. Don’t overtighten anything. Wait until you feel some resistance and then turn it just a little more, maybe an 1/8 th of a turn, no more. It’s been designed that way.
Omegas are designed to be passed on. I have a 1967 Constellation certified chronometer with a calibre 751. I researched this calibre and apparently the engineers designed it to last 265 years. Sympathise with it and it’ll pay you back.

 

Then you should read this:

https://omegaforums.net/threads/water-resistance-with-unscrewed-crown.140296/#post-1909991

 

Thanks!
I really wish I had an X-Ray machine (or a spare crown) to see and feel what really happens inside as it's a bit hard to tell at the moment (that last quarter turn is quite a lot of play, not sure if some kind of O-ring is being compressed during that or what happens exactly: On my 1120-based 2230.50.00 the crown feels much more "lived in" if that's the right phrase, making it much easier.
So far, I haven't managed to get water in any of my dive watches (thank God), but none of them were this expensive, hence my bit of worry

 

Thank you very much: It's very surprising to see that 2221.80.00 withstand the pressure test even with an open crown

I'm wondering how they actually look (after all, the picture "hen" uploaded turned out not to be how Omega crowns look like, according to Al's answer), still it's reassuring to know that there are some kind of extra protection even with an open crown

 

It’s great that you worry and think about it, but the designers are ahead of you. Develop that feel. You’ll be good.

 

I don’t think one can break anything with “finger tightening”, not enough torque. Just tighten it till it stops and forget about it.

 

These questions are always tough to answer because, unlike something like timing tolerances, which can be measured and discussed with objective figures, the responses here invariably will try to talk about the “feel.”

if it helps, my engineer friends do note that the parameters of the things like screws and tools are often designed so that the average person can negotiate them, using common sense, without destroying them. While things like screwing down a crown an knowing when to stop winding a manual watch are helped with some experience, as someone said above, just don’t force it; when it stops, all is good.

 

The case tube is threaded on the inside on most Omega watches. So any diagram that shows external threads on the tube (like Rolex uses), are not accurate. I don't have a diagram of an Omega design, but it's pretty simple...here are the threads on the inside of the case tube:



Here are some damaged threads - this is usually from cross threading:



The outer diameter of the tube is just a straight cylinder, as you can see here - this one is about to be installed in the case:



Here it is installed:



There is one seal inside the crown that rides on the outside diameter of the case - here is one in the process of being replaced:



When you are screwing down the crown, a few things are happening. The seal is being dragged along the case tube as the crown gets closer to the case, so depending on how tight the seal is (how new), how well it's lubricated, etc., that will change the feel of how the crown works.

At the same time, you are also compressing a spring inside the crown - this separates the portion of the crown that is connected to the winding stem (which can't go further into the movement) to the part of the crown that screws down. So the closer to you get to the case, the more compressed that spring will be, and the greater the resistance will be from that spring.

You are also still winding the movement on most Omegas, so you are still moving all the parts inside the watch movement that are related to hand winding.

Hope this helps.

Cheers, Al

 

I think a torque wrench is in order. To about 40 Nm.

Go till it stops. Maybe a slight nudge from there. Less is more. Don’t overthink it.

 

I've broken many things with finger tightening.. especially stems and screw threads in the early days
I now always have to keep myself in check

 

Hi Archer Thanks for the post, I am starting too understand how the seals work now. But isn't there a seal in the crown that compresses against the end of the tube? That would give a much better axial seal compared with the radial seal of the one compressing against the outside of the tube.

 

Me too..

High five...

 

No

 

But yes in Rolex screw.down crowns, I believe.

 

Ask him what he thinks about the triple lock?

 

Yes, Rolex doesn’t appear to trust their design, so they add an extra O-ring that compresses against the end of the case tube.