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Longines Balance staff pivots - are they too flat ?


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10 minutes ago, JohnR725 said:

Pivots burnishing it all down so as nice and even isn't that going to shrink the size of that pivot? Then with shrinkage of diameter isn't that going to be a problem?

It was adding pressure to try to burnish it flatter was what caused my mistake. But now I'm going to have a new balance staff, and new jewels !

Out of interest, does anyone know why top cap jewels are thicker than lower, when they use the same chaton?

Top jewel is 121.11 thickness 0.27mm and bottom 122.11 thickness 0.18mm.  Why not use the same jewel?

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23 minutes ago, VWatchie said:

Not sure how that works for a balance staff though as you would need a same-size chaton with a smaller jewel hole!? If you need to change the diameter of a staff that much I guess it is better to replace it.

That's easy, the chatons are 111.xx where xx is the hole size. These are 10, so I could go to 09

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The story I heard on the thicker top cap jewel (cock jewel) was after lots of practical study, they found that that jewel saw the most impact, so it made sense for it to be thicker. But in reality, I have never ever found a cracked cap jewel on a shock setting, so it seems to have been overkill. But you can't replace it with a thinner one, the spring won't hold correctly- or vice-versa, the spring won't go over the jewel without damaging it.

 

On Jacot too use-

This is a tool I use frequently enough I keep one set up in a vice all the time. I also see young watchmakers who supposedly learned to use it in school come to the shop and are useless on it. Aside from typically using far too short of strokes on both burnisher and bow, they always want to have their face right in the tool with a loupe while using it (possibly why the super short strokes). As I was taught, and continue to do, I get the pivot in place and runner adjusted, checking with a 10x loupe. Then, I get my burnisher in place, and from there it's almost like John said "eyes closed in the dark", that is, I'm not peering at what's going on, just focusing on keeping the burnisher in contact with the pivot (i.e. level and to the left), and listening to and feeling what's going on. I'm sitting in a normal position, looking at the tool, but not up close. Usually pinky and ring finger are resting on the right of the tool, burnisher held the same as one would hold a pen. Pressure is between 250g-1kg, depending on the pivot. It does take some practice to develop a bit of feel, but I have shown folks in 10 minutes how to use it and they are successful.

Edited by nickelsilver
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8 minutes ago, nickelsilver said:

The story I heard on the thicker top cap jewel (cock jewel) was after lots of practical study, they found that that jewel saw the most impact, so it made sense for it to be thicker. But in reality, I have never ever found a cracked cap jewel on a shock setting, so it seems to have been overkill. But you can't replace it with a thinner one, the spring won't hold correctly- or vice-versa, the spring won't go over the jewel without damaging it.

For this movement 30L, the chaton is the same top and bottom 111.10, and the springs are the same 170.03. But the block is different, hence the need for different cap thicknesses. 

(Why do the French have such similar words for top and bottom, (dessus, dessous). Surely at sometime in history a simple typo must have caused disaster?)

Incabloclongines.thumb.gif.bce40f4ecb9d2a1fe6a8941037f47aa4.gif

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On 2/12/2024 at 10:15 AM, nickelsilver said:

On Jacot too use-

This is a tool I use frequently enough I keep one set up in a vice all the time. I also see young watchmakers who supposedly learned to use it in school come to the shop and are useless on it. Aside from typically using far too short of strokes on both burnisher and bow, they always want to have their face right in the tool with a loupe while using it (possibly why the super short strokes). As I was taught, and continue to do, I get the pivot in place and runner adjusted, checking with a 10x loupe. Then, I get my burnisher in place, and from there it's almost like John said "eyes closed in the dark", that is, I'm not peering at what's going on, just focusing on keeping the burnisher in contact with the pivot (i.e. level and to the left), and listening to and feeling what's going on. I'm sitting in a normal position, looking at the tool, but not up close. Usually pinky and ring finger are resting on the right of the tool, burnisher held the same as one would hold a pen. Pressure is between 250g-1kg, depending on the pivot. It does take some practice to develop a bit of feel, but I have shown folks in 10 minutes how to use it and they are successful.

Great advice.

I found an old scrap balance to practice on, and re-dressed my cheapo burnisher,

I too was making the mistake of trying to work looking through the microscope. Following your advice - once set up, sit back and feel and listen to what's going on. You can feel and hear what's happening. I found shaping the end quite easy - as the pivot is sat in a hole in the disc, there's no chance of the balance escaping and getting damaged.  I was so pleased with the pivot end shape and finish I'm not going to bother getting the Bergeon tool.

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On 2/12/2024 at 4:15 AM, nickelsilver said:

The story I heard on the thicker top cap jewel (cock jewel) was after lots of practical study, they found that that jewel saw the most impact

This kinda makes sense.  The top jewel is facing outward from the wrist.  You slap a wall with your wrist going around a corner, the force is toward the top jewel and strong.  On the other hand (same hand actually), if you slap your wrist on the table (when ordering a beer!), your body is part of the shock proofing so less force is seen on the bottom jewel. 

That is my theory and I am sticking with it!

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On 2/12/2024 at 11:15 AM, nickelsilver said:

Usually pinky and ring finger are resting on the right of the tool, burnisher held the same as one would hold a pen.

Probably just me (perhaps I haven't woken up). Anyway, I try to picture how/where you keep your pinky and ring finger (you're right-handed?) and if by "tool" you mean the burnisher (I would assume) but I don't quite get it. I hold the burnisher as I hold a violin bow (was aiming to become a pro when young), which is mostly with the thumb and long finger opposite one another and the other fingers more or less just used to guide the burnisher.

Perhaps you could ask someone to record a short video of you using the tool and publish it on your Instagram. That would be gold!

On 2/12/2024 at 11:15 AM, nickelsilver said:

Pressure is between 250g-1kg, depending on the pivot.

Oh yeah, this is important and took me the longest to figure out!

As can be seen in this video I have my face right up in the Jacot but I will definitely try to just go by feel and the sound to see what it does for me. Thanks for the tip, much appreciated!

 

Edited by VWatchie
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Great, I have to try that! I couldn't figure out your description either. That looks like it could work, it's a bit like playing the guitar, I often support my picking hand with a pinky resting on the body. I guess having played for 30 years helps with fine motoric skills needed in watch tinkering.

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Just to end this thread - I put in a new balance staff and shock jewels. After having 12 hours to run in, on a full wind,  the numbers are :

DD 290°    0s
DU 284°  +7s
CD 235°  +2s
CU 227°  +2s
CL 228°  -5s

After fitting a new staff, I thought I might need to tweak the balance, but I'm more than happy with the numbers.

I think one reason for the good performance is, all the pivots in the gear train are beautifully polished, AND the shoulders of the pivots are polished. Not something I've noticed on other makes.

The original poor performance was due to lack of end shake between the barrel arbor and bridge.

 

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57 minutes ago, mikepilk said:

The original poor performance was due to lack of end shake between the barrel arbor and bridge

But that cannot have impact on performance. The arbor moves when winding only.

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26 minutes ago, praezis said:

But that cannot have impact on performance. The arbor moves when winding only.

Well spotted @praezis - just testing you 🤣.

There was also no end shake in the barrel, which is what was causing the problem. 

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  • 2 weeks later...
On 2/19/2024 at 4:17 PM, mikepilk said:

Well spotted @praezis - just testing you 🤣.

When I make a mistake as a teacher (programming, not watch repairing)and one of my students catches me, I usually say it's my way of checking that they haven't fallen asleep. Of course, I make sure they understand I'm only joking and thank them for their help.

On 2/12/2024 at 10:44 AM, mikepilk said:

That's easy, the chatons are 111.xx where xx is the hole size. These are 10, so I could go to 09

That is valuable and new information to me. Much appreciated!

It wasn't intuitive to find some on CousinsUK, but I found them after a while.

https://www.cousinsuk.com/product/inca-jewel-holes

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