Challenge

I had a challenge presented to me today. An 18-size Hamilton grade 940 pocket watch. Barely running! Needed a balance staff. I had one. As usual, I did a trial fit to see if the staff length and pivots sizes were okay. They were. But as I looked closely at the staff, it wasn’t vertical! Odd, I thought! I fitted the new staff to the balance wheel, trued it, poised it, and watched it to see how it ran. It did, sort of. Upon exploring the watch more closely, I found that the serial number on the balance cock didn’t match the serial number of the movement! The serial number on the balance wheel was different to the movement, and balance cock. Face up, the watch quit. The rim of the balance rubbing under the balance cock. Lowered the balance and then trued it again. Now the rim of the balance was rubbing on the bridge over the train wheels. Raised the balance so it was no longer rubbing, but still stopped face up! Whoever put the hole jewel and cap jewel in the balance cock didn’t seat them, so now, the hairspring collet was rubbing the balance cock, face up. Fixed that. It ran well for a time both face up and face down, but quit again! I had to oil the safety dart on the pallet fork as it grabbed the safety roller on the balance staff on occasion! I think it is now done. I’ll have a better idea in the morning.

Most American made watches can be found to have the serial number of the movement stamped onto the under side of the bridges. This was because, as much as we like to think uniformity among movement components was guaranteed. Not so! This watch is an example of what happens when you mix up the parts! The parts on American movements all had the s# on them so they would stay together during manufacture. The picture is not the problem 940, but a 940 from my collection.