Loose case clamps Omega 284

deloid · Jan 28, 2020

I almost finished this Omega 284 and in testing the stem I tried to fix the mvt in the case and they are a bit shy of the slot so the mvt can move just a bit when tested.
The case looks right , the case back is Omega and in a style I have seen before. I don't think this is the wrong case for this movement. When looking at the slot it looks like it was modified by raising the height with a more shallow slot. I don't have another similar mvt/case to compare it to.
I could add a spacer under the case clamp/spring but I'd like to understand what may have happened.
Thanks for your thoughts.
Dean

redpcar · Jan 28, 2020

Can I see a pic of the movement?

deloid · Jan 28, 2020

Certainly. If you need a better view of the clamp areas please let me know.

redpcar · Jan 28, 2020

Probably best for @Archer or @Canuck to address.
You are the one that disassembled the watch?
You test fit the movement in the case and the stem lined up (centered) in the case tube?

deloid · Jan 29, 2020

Yes this is my work but it is my watch not one of my customers. The movement is properly snug in the case and I had the old stem already inserted but it was a bit rusty so I'm installing a new one. So yes, it is properly lined up.
Dean

Archer · Jan 29, 2020

D deloid
I could add a spacer under the case clamp/spring but I'd like to understand what may have happened.

Why was it tight before (assuming it actually was) and isn't tight now? Who knows - possibly some dirt was holding it more firmly in the case. But I would suspect that previously it wasn't as tight as you have assumed it was.

Cheers, Al

deloid · Jan 29, 2020

I can't remember because I didn't really use this watch. I just peeked in last week and it was filthy. The stem and crown were full of black tar like material. The crown cleaned up but the stem didn't. It is possible that it was loose but the higher cut on the case makes it look like someone didn't know how these clamps work and they cut a new shallow slot to make it easier. On the other hand, I've never run into this problem before so I don't know if cases had those kind of cuts. I could put a spacer under the clamp but I'd like to understand the issue first. Incidentally the clamps look great. Still have spring to them and are at the proper angle.

Archer · Jan 29, 2020

D deloid
I can't remember because I didn't really use this watch. I just peeked in last week and it was filthy. The stem and crown were full of black tar like material. The crown cleaned up but the stem didn't. It is possible that it was loose but the higher cut on the case makes it look like someone didn't know how these clamps work and they cut a new shallow slot to make it easier. On the other hand, I've never run into this problem before so I don't know if cases had those kind of cuts. I could put a spacer under the clamp but I'd like to understand the issue first. Incidentally the clamps look great. Still have spring to them and are at the proper angle.

You have the parts in front of you, so you are the person most well equipped to figure this out. All any of us can do is simply speculate regarding what might have happened (or not happened). If you don't know that it was firmly fixed before, then how are we supposed to figure this out for you?

Generally speaking these don't typically use clamps at all, so right off the start this is an unusual set-up. I can't recall if I've ever serviced one with case clamps - it's usually just the case screws that hold the watch in the case, or in some instances there's a retaining spring that the case back presses down on to hold the movement in place.

deloid · Jan 29, 2020

I understand. I have though found several Omega watches that like this one are rear loading (no removable bezel) and they all, by necessity have these case clamps. They case style and the markings are the same.
This might simply be worn, the clamps may be incorrect or it was modified. I'll just add a small washer/shim under the clamp and that will fix the problem.

Canuck · Jan 29, 2020

That case has a snap back, not a threaded one. You show only one case clamp, but I am assuming there are two. That “dog leg” case clamp is used on cases with a threaded, screw on case back. They are the wrong clamps for that case. You need FLAT case clamps for that case. The dog leg case clamp is necessary when the case has a thread case back, because the threaded portion of the case back screws down INTO the case, and would interfere with flat case clamps, so you wouldn’t be able to get the back to screw down. But with a snap back, since the back fits OVER and not down into the case, those case clamps are wrong. Flat one will hold the movement tight.

deloid · Jan 29, 2020

There are two clamps and I bought this in 1987 from a serious collector. With all due respect though I can find many examples of the 284 with this particular style of case back (styling and snap back) that have case clamps and need to because the bezel is fixed. These can only be loaded from the back so they need clamps.

Canuck · Jan 29, 2020

Please re-read my post. In my opinion, those are incorrect case clamps for that case. I would know better if the watch was on my bench. But flat case clamps should work, and hold the movement tight.

deloid · Jan 29, 2020

I'm so sorry. I did misread your post.
It's hard to see in the photo but these dog legged clamps are only about .2 to .3mm off from being tight. If flat, they would be too high above the notch.

You have given me a better idea though. I might need to make nice clamps that have just a bit more thickness or a shorter drop. Not so easy to find the correct dimensions though. Unfortunately all my forging work is for large metal objects like knives. I haven't done small projects like this.

I think it would be a better restoration with nice new clamps rather than a washer? Yes? No?

deloid · Jan 29, 2020

Wait...I think you mean straight with enough spring to it so it could fit with tension? That would work.

Archer · Jan 29, 2020

D deloid
I have though found several Omega watches that like this one are rear loading (no removable bezel) and they all, by necessity have these case clamps.

Well as I said, some do not use clamps, but internal retention spacers that are held down by the case back - this is a rear loading case with no case clamps or screws used:

If the current clamps you are using aren;t doing the job, it's easy to take some other clamps and provide enough bend to make them work.

ChrisN · Jan 29, 2020

I've seen the clamp you show right at the beginning. It's a clamp used in cases of this era and here's one fitted to a 268 - a customer's watch so just a small area.

Of course, this was a year ago and I can't remember what the case cut-out looked like but, here's the clamp in the parts tray after cleaning. It all just went together.

Not much help, I think, and I'd look at a generic clamp and modify that if the clamp you have is wrong and you don't have a case number for the correct one.

Cheers, Chris

redpcar · Jan 29, 2020

Why not just adjust (bend) the clamps up a little to create the tension you desire?

deloid · Jan 29, 2020

redpcar
Why not just adjust (bend) the clamps up a little to create the tension you desire?

These case clamps are made with high carbon steel and heat treated to have some spring in them. It will bend but then spring back. If I bend it more forcibly it might break or overbend depending on the temper and how it was heat treated. I could anneal them, bend and heat treat again but then I'd have an odd looking clamp and the fit wouldn't be certain. Making new ones would allow me to test for fit with mild steel then make new clamps based on the template. Sigh...
Generic ones as Chris suggested? Maybe.
Slightly bent flats would work but then I'm adding work to the inevitable new owner down the road.
I don't know.

redpcar · Jan 29, 2020

Are you sure about the high carbon steel? Are we talking fractions of mm's here? A love tap on the anvil with your hammer 😉

Canuck · Jan 29, 2020

Depending on the model of Omega, the crystal can have a bearing on how far down into the case the movement sits, and thereby, whether the case clamps will hold the movement tight. You say the stem aperture in the movement lines up with the stem hole in the case. So depthing of the movement may not have any bearing on the movement being loose. The dog leg case clamps may not be as dead hard as you have suggested they are. It might be possible to adjust them so the tips of the clamps ride higher. No doubt the watch didn’t leave Omega, loose in the case.

Loose case clamps Omega 284

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