I'm repairing a 16s Illinois A.Lincoln 9th Model. After reassembling the movement, I noticed the balance action was very poor. Under 10X, I was able to see the top pivot dancing in a large circle???...not actually entering the jewel hole. Rechecked the o.a. length of the staff and compared to the specs. The existing staff is .02mm shorter than specification. The Jewel hole is .13 and pivot is .12... both seem workable to me. I pulled the jewel from a junker A.Lincoln and find that jewel setting seat is is .2mm thinner than the jewel seat in my client's watch. That .2mm is about what I need to gain for proper jewel contact.

Realizing PW people are real sensitive about Rule #1, is it OK to turn down the seat slightly to provide another .2mm drop so the pivot engages the jewel hole? My only other option is to put a friction balance jewel in the junker setting. What is your recommendation?

Bill

Perhaps you have the wrong staff installed...or....the wrong upper jewel?

Thanks for your reply Tony. I measured the existing staff and it's only .02mm under the spec length. I attribute that to wear and normal variation in manufacturing. However, I need to gain at least .2 -.3mm to properly engage the hole in this setting. So, yes to your second question. I don't believe it's the correct setting, (as compared to the setting from my junker). The difference is .2mm in the thickness of the settings. I'm ready to shellack it to a brass and turn the .2mm off and retry. That height reduction should lower the jewel and permit proper pivot hole engagement.

Bill

A couple of possibilities...

The double roller Illinois Balance Staff # 47607 is slightly longer than the single roller version (#47606). it is longer by .02mm.

It could be that you have the incorrect staff (47606), although this would have made fitting a double roller on the staff a real trick...

OR...

You could have taken a upper balance jewel from a M9 that was designed for a DR and are trying to fit it into a SR watch. This arrangement would cause excessive endshake.

If the balance you have is correct, and you can alter the upper jewel to proper specs, in my opinion, you are not breaking "Rule Number 1." You are altering the added part to fit the watch.

IT worked!!! I shellacked the balance jewel to a brass and turned .2mm off the seat. I just reinstalled the balance wheel and ...it vibrates nicely but still has plenty of endshake!

Bill