Seth Thomas Octagon Top Shelf Clock, 1860s.

May 9, 2011 | By | Reply More

This Seth Thomas “Octagon Top” clock was made around 1865, the year the company’s town name was changed from Plymouth Hollow to Thomaston. The movement is marked “Plymouth” but the case label says “Thomaston.” Case height 14 7/16 inches, width 8 15/16, dial minute track 5 1/8 diameter.

This clock has a one-day time and strike movement. Both mainsprings are 3/8 inches wide with loop ends. A common mistake when repairing these clocks is installing new mainsprings that are too strong. It doesn’t take much power to run a one-day clock, and new springs are made from better steel than old ones; so the replacement must be thinner than the original.

In this clock, the original time mainspring had been replaced with a spring 0.0182 inches thick. This had caused about 50% tooth wear to the time mainwheel. I installed a spring 3/8 x 0.014 x 60 inch to reduce future wear.

The original strike mainspring is 3/8 x 0.0173 inches.

The case door is not shown in the photos (the customer didn’t ship the door to me to avoid the chance of breaking the glass). The dial is an excellent repaint job. The hands are reproductions of the original “S T” hands (an S on the minute hand and a T on the hour hand).

See more photos.

Repair job 5304.


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Category: American Clock Mainsprings, American Clock Repair

Last updated: August 31, 2011

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