Is flattening a balance pivot an acceptable Wostep Standard

Alex Hamilton

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Hi All,
I am in a debate over the practice of flattening the domed tip on a balance staff instead of re-polishing it to a domed shape in order to equalize friction. We have all seen a domed balance pivot that has flattened out over time causing loss of amplitude and rate in the horizontal positions.
I was taught to reshape the flat tip back to original condition. My friend says its acceptble in WOSTEP to flatten the the undamaged domed tip to equalize friction.
I really find it hard to believe this is acceptable practice.
Does anyone have any recent knowledge of WOSTEP's standard for this situation. If it is now acceptable, in what situation would this be the preferred repair method.

Thank you
 

DeweyC

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It was not taught when I was there in 2010. However, it is one of the "cheats" high level finshers use(d) when preparing watches for trials. It is not considered permanent.

Since WOSTEP uses modern calibers and new material for instruction, I am uncertain where this discussion would even happen. I suppose it could be an instructor's suggestion that was not part of the curriculum.

I know an instructor at Richemont (since replaced) insisted all the benches and stools be at the same heights despite their adjustments for varied student attributes and preference. He thought they looked more "Swiss" despite the fact that when he went to Neuchatel for training, the first couple hours were/are spent setting up your workspace as you prefer.

I do not think (my books area in storage until next week), that pivot flattening is discussed in Jendritski.

IIRC, Jerry Walker (Phd, ME) once explained to me that the endthrust of the pivot has a very small effect on friction compared to the radius of the pivot. The friction of a shaft is calculated with the rotational speed and radius. This is also the section that experiences fluid drag in the oil.

But that is the extent of what I think I know. And I am not sure Jerry is still around to defend himself from any misunderstanding I may have.

From a practical standpoint, unless aiming for dead flat, how would you measure so that you can make corrections? What about changes in endshake? How do you avoid changes in sideshake when you reburnish the cylinder to remove the bur raised by working on the pivot end?
 
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karlmansson

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I think it's always an interesting thing to consider if you are to keep things as close to original as possible or to use improvements where possible. Even using old school lubrication seems to be advocated in some circles, so that the movement is time-authentic down to the last detail. I a watch had flat pivots to start with you migh consider putting a flat on a new staff to make it similar.

George Daniels proposes grinding an eve so slightly off center divot into the cap jewel to ensure that the balance always has the same side contact regardless of position. The end result is the same as with flattening the end of the pivot: to equalize amplitude in horizontal and vertical positions. then again, Daniels was notorious for leaving a lot of thinking up to his readers, so maybe this is not earnestly meant as a viable technique.

Never went to WOSTEP so can't say what they would have to say on the matter.

Regards
Karl
 

praezis

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I do not think (my books area in storage until next week), that pivot flattening is discussed in Jendritski.
He did, e.g. here:
Zapfen_flach.jpg

But it rather looks like a thank you for his sponsor B. Not forgetting to mention, to do it on medium quality or less watches only.

Frank
 
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Tom McIntyre

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I always though that playing with the curve of the pivot on the bottom end only was a "cheat" for trials to slow down the dial up position.
 
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D.th.munroe

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Vulcain did a similar thing to prior to Daniel's but the opposite way more like a cone on the inside of the cap jewel.
Dan
 

DeweyC

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I always though that playing with the curve of the pivot on the bottom end only was a "cheat" for trials to slow down the dial up position.
I think it's always an interesting thing to consider if you are to keep things as close to original as possible or to use improvements where possible. Even using old school lubrication seems to be advocated in some circles, so that the movement is time-authentic down to the last detail. I a watch had flat pivots to start with you migh consider putting a flat on a new staff to make it similar.

George Daniels proposes grinding an eve so slightly off center divot into the cap jewel to ensure that the balance always has the same side contact regardless of position. The end result is the same as with flattening the end of the pivot: to equalize amplitude in horizontal and vertical positions. then again, Daniels was notorious for leaving a lot of thinking up to his readers, so maybe this is not earnestly meant as a viable technique.

Never went to WOSTEP so can't say what they would have to say on the matter.

Regards
Karl
Daniels was a prolific experimenter for sure. I wonder how measurable the difference ws between this and his normal staff geometry. Each of us develops a specific stye to our staffs that is pretty unique to us. But after a while our pivots are consistent.

So I would imagine at his level of experience, his pivots are very uniform. I wonder what drove him to such a labor intensive procedure.

Again, all my books are not accessible until after next week (and some time after that!).

Thanks Karl!
 

DeweyC

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Vulcain did a similar thing to prior to Daniel's but the opposite way more like a cone on the inside of the cap jewel.
Dan
Dan,

This almost sounds like a means to correct for inconsistency to the manufacture of the pivot ends. To ride at a specific radius and "ignore" how the actual pivot end was finished.

Do you know why they did this?
 

D.th.munroe

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I believe they did it for the same reason Daniels did, just to try to equalise vertical and horizontal pivot friction for a closer rate but it does ignore the end of the pivot.

I don't remember what book that was in, a more common book though, DeCarle maybe it was mostly about not to put them upside down they are supposed to have the curved side in.
Here is a post with some though
 
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Al J

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Does anyone have any recent knowledge of WOSTEP's standard for this situation. If it is now acceptable, in what situation would this be the preferred repair method.

Thank you
I can't speak to who may or may not approve of this method, but it's not something I would imagine myself doing.

If there is a difference in amplitude between horizontal positions, it's usually because one end is worn flatter than the other, typically the upper pivot in my experience. I always burnish it round again, rather than flatten the other end.

Off the top of my head, I can't see a situation where flattening the rounded pivot would prove more useful than rounding the flattened pivot. I suppose if one had excessive amplitude it might be some sort of work around, but in my view the source of the excessive amplitude should be found and solved instead of this.

Cheers, Al
 
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karlmansson

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I can't speak to who may or may not approve of this method, but it's not something I would imagine myself doing.

If there is a difference in amplitude between horizontal positions, it's usually because one end is worn flatter than the other, typically the upper pivot in my experience. I always burnish it round again, rather than flatten the other end.

Off the top of my head, I can't see a situation where flattening the rounded pivot would prove more useful than rounding the flattened pivot. I suppose if one had excessive amplitude it might be some sort of work around, but in my view the source of the excessive amplitude should be found and solved instead of this.

Cheers, Al
Isn't it a way to equalize amplitude in horizontal and vertical positions?
 

gmorse

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Hi Karl,
Isn't it a way to equalize amplitude in horizontal and vertical positions?
That's my understanding of it, but I think it would be a mistake to assume that the pivot would be completely flattened; like all the adjuster's arts, the degree would be very subtle, perhaps a single stroke of the burnisher would be sufficient to produce the desired effect.

Regards,

Graham
 
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Al J

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Isn't it a way to equalize amplitude in horizontal and vertical positions?
I suppose, but that would mean you see differing amplitudes in horizontal and vertical as a problem that needs to be solved.

Of course you know it's natural to have higher amplitudes in the horizontal positions due to the smaller frictional loads, but this isn't a problem in itself with regards to getting good timing results. But I suppose it depends on what sort of result you are after.

I regularly exceed the requirements set out by the various brands for timing, so Delta, average rates, etc. One could say the brands have very loose tolerances, and in some cases that is true, but when I can take a 60 year old movement and exceed the requirements for all timing parameters (COSC, METAS) for new watches with fancy escapements, silicon balance springs, etc., without doing things like flattening pivots, I'm not sure what else needs to be done.

Cheers, Al
 
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