Hairspring fitment

[Nora]

Are hairsprings from withing the same model interchangeable? I'm not concerned at this time with correction for beat error. Only is it possible to remove a damaged spring and directly swap it out for one that is in a parts watch. It is repairable, however it's above my skill set at this time.

Thank you in advance.

Nora

[nickelsilver]

They aren't really interchangeable. On modern watches the balances are made and then grouped by inertia, a dozen or so groups. The hairsprings are grouped similarly, then they are matched up. The grouping forms a sort of bell curve around the "standard", so most springs and balances fall somewhere in the middle, but that doesn't help much. If you have a balance with screws you have some adjustment, either adding washers or removing material from the screws, with solid balances there is little adjustment you can do.

 

On older watches the springs were individually fitted to each balance. Again, the balances are nominally the same, but as you'll see when you get to using timing washers, very very little difference is needed for a balance to not want to mate with a spring that wasn't intended for it. It does work sometimes though.

 

You can try, sometimes you get lucky, but no, they aren't interchangeable.

[Nucejoe]

There you are,  plus some information from the assembly proceedure.

Furthermore, the answer to your question is " mostly yes " with the exception of a small section of the curve mentioed above, expectedly much higher chance of success with newer models.

By yes I mean you are highly likely to have success, specially with models.

What caliber are you working on?

 

 

 

 

 

 

[watchweasol]

Hi the probability factor of the springs being the same within the family group will differ, If you get a watch caliber for caliber the likely hood of it working is better but not perfect.

[Nucejoe]

Within the normal distribution Nickelsilver spoke of, there is a regìon of compatibility of the HS and wheels.

Old wheels did not all weigh the same, that is their inertia distribution graph showed big variance. As production know-how improved, the question of standardisation became inexpensive to address, thence we had narrow inertia distribution of the wheels, (small variance). This means improvement of compatibilty region.

Compatibilty means the two can be vibrated to produce the desired or design beat.

In short if donor and receiver are of the same caliber, compatibilty is more probable to 95% or more.

Practically just give it go, if the balance complete runs fast free sprung, nothing you can do in case of anulare wheel.

If it run slow, you are on and at worst may have to cut to shorten the active length of the HS to get the design beat.

 

 

[JohnR725]

it depends upon your balance wheel as to whether you can just swap a hairspring or not.

If it was an American pocket watch for instance the answer would be yes. American pocket watches if you look in the parts book had hairspring is available separately. That's because the hairsprings are made to very exacting specifications with the over coil and it's too hard to vibrate and then bend that. Not that they didn't do it at some point in time it was easier to make the hairspring first. Then the balance wheel has timing screws which were also available.

then typically with wristwatches at least up until now they hairspring is vibrated to each and every balance wheel. There was enough variation with the balance wheels and even just pinning the hairspring that they have to be vibrated together. which is why typically on the parts list it's a balance complete.

13 hours ago, nickelsilver said:

They aren't really interchangeable. On modern watches the balances are made and then grouped by inertia, a dozen or so groups. The hairsprings are grouped similarly, then they are matched up. The grouping forms a sort of bell curve around the "standard", so most springs and balances fall somewhere in the middle, but that doesn't help much. If you have a balance with screws you have some adjustment, either adding washers or removing material from the screws, with solid balances there is little adjustment you can do.

then the quoted paragraph above another thing that helps today is having a floating stud and regulator. previously on watches your regulation range was limited and now you do have considerably more range. but for timing purposes everything really asked be really really close or you're going to be really often timing.

So ideally to get this to work your balance wheel has to have screws unless you have enough hairsprings you can find one that's slow for the balance wheel then you can take weight off a screwless balance wheel.