Loss of Amplitude Due to a Flattened Balance Staff Pivot

Flattened Balance staff

Written By Alex Hamilton

Alex Hamilton is a watchmaker, collector of fine watches and writer of all topics in the study of Horology.

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Flat Pivot Tip

I am adjusting a 922b. Dial down I had a rate of +7 and a amplitude of 306. Dial up the rate was +13 with a amplitude of 289. Since the rate is faster and amplitude is slower in the DU position that tells you the problem is more than likely in the upper balance jewels since this is where the friction is in the DU position.

This is the pivot tip of the upper balance staff. You can see in the picture how it has flatted out,probably due to being allowed to run for too long with either no lubrication or old lubrication.

Since this flattened pivot is what is spinning on the end stone in the DU position, this is causing the amplitude to drop and the rate to speed up because of the added friction.

Flattened Balance staff

Here is the pivot tip on the lower part of the balance staff. notice the slight domede shape.

Flattened Balance staff

To fix this problem you use a Bergeon 5482. This tool has a small opening with a domed jewel inside. You mix a little Diamantine power mixed with oil, insert it onto the flattened tip and polish it until the pivot is domed the same s the other side.

Bergeon 5482

After re-lubing the end stone and re assembling the balance the horizontal rates amplitude are now the same and I can move onto the vertical positions for furthur adjusting.

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