Reply To: Runaway waltham

[Bob Tascione]

Hi Fred,
I don’t want you to think that I was suggesting making those adjustments. I just wanted to post other things that might be happening and what people often do to tackle the problem. If the stuff that I mentioned in my earlier post checks out ok then we could go from there. One thing that I don’t recommend is to add or subtract weight to the balance unless its mass has been altered by someone in the past. This even applies to poising if possible. Except for fine adjustments of the rating screws the balance should never be altered to match the hairspring. The hairspring should be made to match the balance. Looking at the chart that Steve posted (Thanks Steve…nice file!) you can see that adjusting the rating screws for a “one hour fast in 24 hours” rate is pushing it. If you figure that one full turn either in or out will give you a rate change of 2 minutes a day you can see that you’ll need about 25 turns or so to correct that hour a day issue. I’m not sure what the threads per inch would be on a Waltham rating screw but if we guess somewhere around 110 to 120 tpi then you’re looking at having to move the screws out something like .187 to .250 (3/16 to 1/4 inch). That’s a bunch!
I often got lucky swapping NOS hairsprings for American watches when needed. If they were too far off I would usually grab another one and try it until I got within an acceptable range. But I was fortunate to have an abundant selection of hairsprings on hand that I had accumulated over the years. If I didn’t have what I needed I had other watchmaking friends who probably did!

Anyway, thought I should clarify my earlier post as it may have been a bit confusing.
Please let us know what you come up with Fred!
and of course….have fun,
Bob