American antique one day spring driven clocks often have mainsprings much stronger than necessary. This can cause severe wear to the mainwheel teeth. Shown here is a Waterbury walnut case kitchen or shelf clock, ca. 1880. The movement has a patent date of September 22, 1874.
The movement has the original strike mainspring of 1/4 inch wide by 0.019 inches thick. Yes, this spring is very thick, but it is not very “springy” and does not provide much force, so there is NO wear on the mainwheel teeth.
The time spring was a replacement of 1/4 inch wide by 0.0157 inch thick. There is about 30% wear to the time mainwheel teeth. I replaced it with a mainspring 5/16 inch wide by .0125 inch thick by 45 inches long (actual specifications: 8 mm x 0.33 mm x 1150 mm). This spring provides plenty of power, enough for the movement to run about 48 hours on a winding. This spring is part no. PM-CS510 from The PM Company. They have a great online and printed catalog, including hard to find parts for Swiss travel clocks.
My job 4365
The movement is designed to accommodate 5/16 inch wide mainsprings.
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