Gross balance wheel adjustment question

[D N Ravenna]

I have an old Swiss PW which was recently re-staffed. The 'smith did an excellent job, but warned me that it was about 45 seconds slow per day with the regulator in the middle.

I still have to fit on the hands and find a crystal, so it may be possible that I can use the regulator. But it got me thinking, How does one lighten the balance wheel on a slow watch?

The watch is a mid-grade model with no mean-time screws. So that is not an option. So, what is the acceptable way to lighten the balance wheel? Replace two screws 180 degrees apart with lighter ones? Replace four screws 90 degrees apart with lighter ones? Due to the age of this one, it will most likely mean that I will have to use a balance screw cutter and re-poise the balance wheel.

I would sure like to hear your ideas!

Regards and thanks in advance,

Dan

[D N Ravenna]

I have an old Swiss PW which was recently re-staffed. The 'smith did an excellent job, but warned me that it was about 45 seconds slow per day with the regulator in the middle.

I still have to fit on the hands and find a crystal, so it may be possible that I can use the regulator. But it got me thinking, How does one lighten the balance wheel on a slow watch?

The watch is a mid-grade model with no mean-time screws. So that is not an option. So, what is the acceptable way to lighten the balance wheel? Replace two screws 180 degrees apart with lighter ones? Replace four screws 90 degrees apart with lighter ones? Due to the age of this one, it will most likely mean that I will have to use a balance screw cutter and re-poise the balance wheel.

I would sure like to hear your ideas!

Regards and thanks in advance,

Dan

[Don Dahlberg]

There are many ways to fix this problem, but you want to find the correct one. Too many people fix one problem by creating another compensating problem.

If this is a split balance, were the two half rings bent outward away from the staff? Check to see if the balance is true in the round and flat and that the splits are reasonable sizes.

Wind the watch such that the balance is doing about 1 1/8 turns so that there will be little change in rate over the pendant positons. Check the rate dial up and dial down and pendant up. If the rate is slower in the pendant position than in the dial position, then check to see if the regulator pins are too far apart. You want them as close together as you can without binding the hairspring. Bringing the regulator pins closer together will speed up the rate in all positions, but more in the pendant positions than in the dial positions.

If the dial up and dial down positions are far apart in rate, then there may be something wrong with one of the pivots or one of the jewels, although this usually causes a fast rate on the problem side.

When you are sure there is no other reason for the rate, then you can take weight off balance screws. Make sure the balance is poised. If not, poise it by removing weight. If it is poised, then you will have to remove weight from opposite sides from screws either next to the arms or 90 degrees from the arms. Removing weight form other screws will change the temperature compensation.

Remember that removing weight is not easily reversed, so check all other factors first.

Good luck,

Don Dahlberg

[D N Ravenna]

Thanks for the tip Don!

;-)

Dan

[D N Ravenna]

Thanks all! I should state that the watch was compentently cleaned. I have yet to fully assemble it. My question was simply posed as a thought I had in passing. Nothing has been attemped nor will be until the last parts are in.

:smile:

Dan