Dave taught me to assemble the entire rotating assembly and do free spin and free balance testing before I installed the pallet fork.

The free spin checked out and the balance responded nicely to the puff test... except...

When I puffed the balance and observed... the escape wheel would all of a sudden start to oscillate and synchronize with the balance wheel rotating back and forth.

A few seconds in the demag and all is well. The balance toggles for well over 30 seconds before coming to a stop and the escape wheel no longer seems to be inspired by the balance wheel.

This is a good test to make and should be done on every repair. The movement should also be tested dial up and down as well as vertical and on a 45 degree angle from vertical. Observation should be made when the balance comes to a stop that it is very smooth and free. This is also a perfect time to check for initial beat by observing the location of the roller jewel between the banking pins with the balance at rest. It should be centered or very close to it.

Roger,

"This is also a perfect time to check for initial beat by observing the location of the roller jewel between the banking pins with the balance at rest."

Could you explain further on banking pins? I have run into a few movements were you can tell someone has messed with the screws that move the banking pins around. Is there an ideal location for them to be in - as a starting place and adjust in either direction. Also, it seems a tad perplexing that the banking pins have the ability to be adjusted to 180 degrees (all the way towards or away from the roller jewel on the balance wheel). Is there a reason behind a full range of movement for them because it greatly effects the snap of the pallet fork.

Sorry - but those banking pins have my number

Jon,

Banking pins are adjusted for lock and drop on the pallet jewels. They should rarely, if ever need adjusting, but as you have observed they are frequently disturbed. There are two holes in the plate that allow observation of the 'bite' of the pallet jewel to the escape wheel tooth. The amount of 'bite' varies a bit between makes and model. I would suggest observing a known good movement so you have an idea what it should look like. You can see it with the watch running, but it takes some practice since it is a bit like a strobe effect. The pins are eccentric or off center so when you turn the adjusting screw you are adjusting how far the pallet arm can travel before it hits the pin and thus increase or decrease the 'bite' on the pallet tooth. This can be a tricky area to get comfortable with. I don't know if I've answered your question, but let me know if I need to clarify.

The banking pin adjustments described by Roger compensate for the positioning of the entrance and exit pallet Fork jewels that themselves are not necessarily symmetrical to the alignment of the roller jewel pin when it is centered to the imaginary line through the balance wheel pivot axis and that of the escape wheel axis meaning the pins may look "off-center".

Good "Beat" is very closely related to centricity of the roller pin, and can be "fine tuned" by tweaking the correct let off allowed by the banking pins which are best left as factory-adjusted to the originally assembled escape wheel and pallet fork . The banking pins should only require adjustment when ANY changes are made to those two parts .

The banking pins should not be moved as Roger has alluded to, but most have been. You should set the clearance between the roller jewel and the horn of the pallet fork, once this is set to the correct clearance, then you adjust the lock and draw by way of moving the pallet jewels in or out to get the correct depth. On most watches the depth should be about 1/3 of the width of the escape wheel foot, although through my own experience this does vary slightly with some makes. Because of the extra time and trouble it takes to reset pallet jewels most people use the short-cut of moving the banking pins.

Regards,
Bila

Thanks for all the information - Gents...

Greatly appreciated