Question about poising

[CaptCalvin]

Hi. I've recently decided to try watch adjusting. It is my understanding if there is a heavy spot on the balance wheel that the fastest positions and slowest positions would flip when the watch is run with low amplitude vs high amplitude. My question is, if the balance itself is perfectly poised and that if the fault lies with the hairspring only, would it be reasonable to expect that no such flip would occur?

[Tmuir]

I'm not quite sure I understand what you are saying.

Are you talking about the fast and slow adjustment marks on the balance bridge?

If the balance is not poised positional accuracy will be all over the place as the heavy spot will always want to go down so depending on how the watch is being held, Crown up , Crown down etc will impact the accuracy.

If  you hairspring is not correct, out of round, out of flat, coils stuck together either by magnetism or oil, other than the coils stuck together which will always make teh watch run fast the other issues may make it run fast or slow too and could change due to how the watch is held.

For example if the hairspring is not flat it may catch on the bridge or center wheel when the watch is held in one position but not another.

[Delgetti]

I think the flip would also occur as it is a result of the behavior of the complete system, not of the balance wheel only. Do you know this blog, very helpful:

https://adjustingvintagewatches.com/category/dynamic-posiing/

[CaptCalvin]

You see, from what I understand, the flip occurs because when the heavy spot on the balance is orientated downwards it is impulsed in the ascending supplementary arc and resisted in the descending at low amplitude but at high amplitude the heavy spot travels over the top and this effect is reversed. But if the balance has no appreciable heavy spot and the error is from the hairspring why would this reversal be observed? The center of gravity of the hairspring stay on relatively the same side regardless of amplitude?

[nickelsilver]

You see, from what I understand, the flip occurs because when the heavy spot on the balance is orientated downwards it is impulsed in the ascending supplementary arc and resisted in the descending at low amplitude but at high amplitude the heavy spot travels over the top and this effect is reversed. But if the balance has no appreciable heavy spot and the error is from the hairspring why would this reversal be observed? The center of gravity of the hairspring stay on relatively the same side regardless of amplitude?

How do you know that what appears to be a poise error is from the hairspring?

High grade watches used to have poised hairspring collets, and generally overcoil hairsprings. Modern watches almost universally have even better collets, with attachment of the spring inducing no stress at either collet or stud, and often some supplemental heat treatment of the terminal curve, which altogether gives performance like an old overcoiled piece.

The hairspring alloy makes a difference (big) in performance as well, a Nivarox 3 will never perform like a 1, and even the 1 grade has better and worse springs.

But a clear poise error is a clear poise error. Often I've spent time on the poising tool to just undo half of it on dynamic. Smaller calibers are always worse than larger, a LeCoultre 101 can be a real bear (factors of scale, hairspring collet is always proportionally bigger on smaller pieces). But all experience and such goes out the window sometimes; had a 104 (about 1mm bigger than 101) that had a vertical delta of 80+ seconds, an hour of nerve crushing work on the poising tool and it was under 30- which is almost unheard of on these. I only believe it because I saw it.

[CaptCalvin]

The alloy I'm dealing with is in fact anachron (top grade 7750) so no issues there. I don't know if the error is mainly hairspring, which is why I ask if my hypothesis is a viable way of determining whether or not most of the fault lies with the balance or hairspring. When I remove the upper pivot cap and hole jewels, I observe that the pivot has a noticeable tendency to spring to one side of the setting, towards 6 o clock direction specifically. Incidentally the fastest position is crown right. Might be a relationship there. I know the hairspring is inducing some degree of error, but not sure exactly how much and just want to find ways to get a clearer picture. I want to make sure I got everything sorted out with the hairspring the best I could before I go and attack the balance.

[nickelsilver]

What is your timing in 8 vertical positions (and at what amplitude)?

[CaptCalvin]

Back of the watch facing towards me, full wind, starting with the crown down position, each measurement made at 45 degree rotations counter clockwise:

-2 @292

-1 @288

0 @284

0 @299

+2 @297

+3 @301

+4 @288

+2 @ 288

Same thing, but at low wind:

-15 @165

-9 @165

-11 @164

-15 @162

-21 @142

-22 @160

-20 @158

-11 @ 167

[nickelsilver]

That's a pretty great rate, but there is a little error, more evident as would be expected at low amplitude. Just try out moving the spring in the direction to get it centered and see what the effect is. If it were me I would leave it, I would bet you are at a similar delta and overall rate as your full wind at 24h. Plus it's an auto so it spends most of it's life far from the 24h mark. But it looks like a very slight poise issue, and would require just a tiny removal of material.

One problem with chasing "perfection" is every time you manipulate the balance, there's a risk of introducing a new error, from slightly tweeking the hairspring to a microscopic piece of dirt getting in a pivot, or on the roller jewel, or the lower pivot brushing the fork slot (oil on the slot), to a half a dozen other things. 7750 is pretty robust and tolerant, it's worse as you get smaller (0.06mm pivots can drive you to drink).