Cal. 321 vs. 861 Maintenance

ChrisN

I assume you have a 321 with a damaged hairspring and, to me, you have a few options:

ChrisN

If there really is no other way, then you buy a flat hairspring and form the overcoil at the bench. You're down to 5-10% of watchmakers now and it will be expensive. You can still buy steel hairspring blanks in a huge range of stiffness values for about $1 each, although calculating the stiffness you need is not simple at all, and that's the easy part...

Cheers, Chris

Screwbacks

mine is still in immaculate condition, feels smooth and winds flawlessly. 😉
oh no. i cant put a toyota engine in a ferrari.😁🤦

ChrisN

Good to hear that your's is fine👍

As far as I'm aware, all these steel springs started out flat in period although things have changed a bit these days. The way you make them is to draw a piece of steel wire through a die (probably diamond) so that it comes out at the right cross section and is polished. Now, you have a straight piece of steel wire and you wind a few of these into what looks like a mainspring barrel (so, a bit like winding a mainspring in by hand - which we don't usually do for various reasons!), until the "barrel" is full, then close the barrel with a loose lid. Each spring is being spaced by the other springs.

They made a lot of these and piled the "barrels" one on top of another and applied pressure to keep them all pressed together so each spring is pressed down against the lower part of the "barrel", then heat, quench and the spring will come out set in a spiral. Then you can temper and blue them. What you're left with is a hairspring coil but flat, and then the watchmaker (some specialist in forming overcoils) makes the overcoil and pins to the collet and stud. So, what I'm describing the watchmaker doing regarding forming the overcoil is what was done in period. I don't know any way that the overcoils were formed within the manufacturing process but am happy to be corrected as it's not something I've gone into in detail.

The only issue is whether the quality/specification of the flat hairspring coils available now is worse than those made by Omega (or their supplier) in period. I very much doubt it and wouldn't think this would be the Toyota/Ferrari argument, personally. Still, better to repair like this than have a non functioning watch although, I'd agree, that always best to get the correct OEM parts.👍

Cheers, Chris

ChrisN

...............Change from Breguet to flat hairspring.............

maxbelg

I thought the change was because of the increase in beat rate from 18000 to 21000 and therefore not needing the Brequet overcoil so much anymore seeing as accuracy was OK in various positions, cost being an added benefit. I'm happy to be corrected if this info is wrong.

ChrisN

The more typical change is from 18000 to 19800 or 21600 in this period and this increase in beat rate is probably due to oil improvements. Not many companies use a 21000 beat rate. Again, I'm no historian but it would make sense that the better oil protection with, possibly, better surface finish and hardening would allow for the increase in beat rate without compromising service intervals.

Beat rate increase doesn't necessarily go with a change to a flat hairspring and that's why I gave the examples above rather than just 321 to 861. I have never seen this linking written down in any reference document but, you may see it on watch blogs as they are never peer reviewed. There was a lot going on in that period and I'm not saying that the two aren't partly linked, though.

Cheers, Chris

watchtinker

Hi Chris,

the only in depth analysis of the differences between the caliber 321 and the caliber 861(both from a structural and a performance standpoint) I am aware of is contained in a book published five years ago, which I believe has also been referenced in some watchmaking schools in Italy:

https://ilmiolibro.kataweb.it/libro/scienza-e-tecnica/94315/tempo-imperfetto-3/?refresh_ce

Regards,

Maurice

stefman

I’m curious, is it common for the hairspring to break? What would be the conditions for it to break?

ChrisN

You shouldn't see many broken hairsprings. If you consider that the balance is supported at the upper and lower pivot and the hairspring is supported at the collet (on the balance) and at the stud, the spring is unaffected by anything except its own mass (plus the balance impulses), which isn't big relative to its strength. If a balance pivot breaks, which is not usual especially with shock protection, then the balance could try to extend the spring and break it. So, yes, I suppose it could be down to a hard shock.

I don't believe that any of these steel springs are working above the endurance limit so, fatigue is not an issue. The "endurance limit" is the amount of stress/strain above which you need to consider fatigue. Below that level, you can apply infinite cycles of load/stress/strain and it will never fail in fatigue. This is why you can rely on 100 year old car parts made from steel but you can't do that if they are aluminium as there is no endurance limit for aluminium - it doesn't matter how low the applied loads, eventually it will fail in fatigue.

If you see a broken balance spring, then it would usually be when the watch is open and someone is poking about or working on it. You often see damaged/deformed hairsprings but still, very unusual to see them broken. This is the worst sort of damage to see, where the outer coil of the hairspring is twisted and out of shape and it's usually close to the regulator pins... Oddly, big corrections I showed in another post are easier to do but, this sort of twisted damage is very hard for me to resolve well.

Cheers, Chris

ChrisN

You shouldn't see many broken hairsprings. If you consider that the balance is supported at the upper and lower pivot and the hairspring is supported at the collet (on the balance) and at the stud, the spring is unaffected by anything except its own mass (plus the balance impulses), which isn't big relative to its strength. If a balance pivot breaks, which is not usual especially with shock protection, then the balance could try to extend the spring and break it. So, yes, I suppose it could be down to a hard shock.

I don't believe that any of these steel springs are working above the endurance limit so, fatigue is not an issue. The "endurance limit" is the amount of stress/strain above which you need to consider fatigue. Below that level, you can apply infinite cycles of load/stress/strain and it will never fail in fatigue. This is why you can rely on 100 year old car parts made from steel but you can't do that if they are aluminium as there is no endurance limit for aluminium - it doesn't matter how low the applied loads, eventually it will fail in fatigue.

If you see a broken balance spring, then it would usually be when the watch is open and someone is poking about or working on it. You often see damaged/deformed hairsprings but still, very unusual to see them broken. This is the worst sort of damage to see, where the outer coil of the hairspring is twisted and out of shape and it's usually close to the regulator pins... Oddly, big corrections I showed in another post are easier to do but, this sort of twisted damage is very hard for me to resolve well.

Cheers, Chris

Archer

Not common at all. If a balance spring is broken, it certainly won't go undetected, as the timekeeping would be very bad if the watch even ran at all.

Although I've seen many mainsprings labeled as unbreakable, I've not seen the same claims made for balance springs...these are some mainsprings that claim to be unbreakable:



Of course they are not really unbreakable, but compared to the blued steel mainsprings, they last much longer.

Certainly newer alloy springs are more durable than the old blued steel springs, and that applies to balance springs as well as mainsprings. The old blued springs can rust, get pitted, etc. making them weaker and more prone to failure. If a balance spring is going to break, it's usually near the stud, and personally I've had cases where the spring needs adjusting, and as soon as I touch it, it snaps at the stud - this indicates it has been heavily manipulated in the past, and has work hardened.

Cheers, Al

SeaSubRod

How much more difficult/expensive is it to service/fix a cal. 321 vs. 861?

In the market for my first Speedy and long-term maintenance is a concern. I prefer the cal. 321, but have been warned that servicing it might be a nightmare. Any guidance/tips would be welcome. Thanks mates!