Does Anything Looks Suspicious about This Tube?

[nyyankees]

I was just looking at this close-up of the tube on my Exp II and it looks different than the tube I had on my datejust in that the thread does not go up all the way. This is a D serial Exp II. Anything unusual about this?

Thanks for your comments.

Jim

[astcell]

Is there a rubber seal in the crown which covers that spot?

[padi56]

Originally Posted by nyyankees

I was just looking at this close-up of the tube on my Exp II and it looks different than the tube I had on my datejust in that the thread does not go up all the way. This is a D serial Exp II. Anything unusual about this?

Thanks for your comments.

Jim

Looks fine and perfectly normal on twinlock check picture below of a few crown and tubes and O/ring seals.

[bodybump]

Originally Posted by astcell

Is there a rubber seal in the crown which covers that spot?

Thats what im looking for too robert...

[Tools]

That little extra space at the top does two things..

First it allows the crown to be pressed down and more aligned prior to starting the threads...it helps prevent cross threading..

Second, it gives the "O" ring inside the crown a bit more clearance away from the threads so there are no sharp edges to mess it up..

It probably was not incorporated in early tubes because of the available technology at the time.

[nyyankees]

Thanks Guys. I love the expertise here! It can't be found on any other forum

[JJ Irani]

Originally Posted by astcell

Is there a rubber seal in the crown which covers that spot?

Yes, each and every crown has a built-in rubber seal that presses down on the top of the stem when you screw down the crown.

At the time of service, the entire crown is replaced for a new one.

JJ

[marshallr47]

It looks just fine to me and you are right, great folks on this forum.

[astcell]

Originally Posted by JJ Irani

Yes, each and every crown has a built-in rubber seal that presses down on the top of the stem when you screw down the crown.

At the time of service, the entire crown is replaced for a new one.

JJ

Wow, must be tough to keep a watch authentic after 7 or 8 visits to the shop!

[Lol-x]

I love that fine detail technical information.

[unclesallie]

man, you guys are GREAT! thanks.

[CVerKuilen]

From what I was taught in watchmaking school, the crown is to be about .1 mm from the end of the tube, or about the thickness of a sheet of transparency plastic for overhead projectors. This does a few things:
Allows the crown to be turned without fear of it touching the tube while winding, while keeping it close enough so the part of the crown that seals with the gasket in the case tube stays sealed to prevent any dust or ambient moisture in the air from entering the case. I could imagine this may not be taking place in the image shown.
The last, and possibly most important reason is that the crown has a hexagonal sleeve that compresses when the crown is screwed in. This sleeve has a travel of 1.5 to 2 mm. Once this travel is exhausted, any further inward motion of the crown (screwing in more, or even the crown being struck) results in 2 very bad things occurring: first the winding stem bottoms out at the front, piercing into the mainplate and heavily damaging one of the most expensive components of your movement. The next occurrence may or may not happen on Rolex movements, but on 2824's, 2892's and similar, the pilot of the stem will crush the tube the center seconds post goes through, stopping the watch and requiring an expensive repair.
So IMHPO, the crown should be no more than .25 mm from the tube when unscrewed.