Here’s a Waterbury oak “kitchen” shelf clock from around 1910 to 1920. It has an 8-day movement that strikes the hour and half-hour. It appeared to be a routine repair job, but turned out to be challenging.
The time mainspring was a replacement that was WAY too strong. Normally a Waterbury clock like this has thin mainsprings, to reduce wear in the movement. Typically, these mainsprings are about 0.015 inch thick. Here, the time mainspring was 0.018 inch thick. Since the force the spring provides is proportional to the cube of the thickness, this spring was providing almost twice the force of the original mainspring. I replaced it with a mainspring 3/4 inch wide by 0.014 inch thick by 108 inches long (Merritt’s Antiques MS301).
During repair, I found that the time second wheel came close to touching the click on the time mainwheel. I adjusted the height of the second wheel, and thought all was well.
I assembled the movement after final cleaning, and started to wind the time mainspring. When I took my hand off the key, it unwound again. Rats! The mainwheel arbor was not tight in the ratchet hub. I took the movement apart, drove the arbor out of the mainwheel. I tried Locktite, but that didn’t hold. I inserted two thin steel wires in the hole in the hub, then drove in arbor, and it was very tight. I reassembled the movement, and it now runs well.
The pendulum takes a wonderfully wide swing, showing that the 0.014 inch thick mainspring is strong enough. The original strike mainspring is 3/4 inch wide by 0.015 inch thick.
Repair job 8041. I polished the pivots and installed 14 bushings. Most clocks have brass movement plates, but this one has steel plates with large brass bushings having the pivot holes in them. I installed #3 KWM-size American System bushings in the large bushings. I replaced the flat steel clicksprings (which often break) with round steel clicksprings. I installed new wires in the escape wheel pinion. The movement plates were bowed, I flattened them. I made a new brass door latch.
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