Seth Thomas Sentinel #1 Tambour Mantel Clock

Here’s a Seth Thomas clock I repaired called “Sentinel #1”. It has a mahogany case, 16 3/4 by 9 inches with a 5″ dial and “ST” hands (the minute hand has a letter S worked into its design, and the hour hand has a letter T). The movement is No. 89 8-day, striking on a cathedral gong. The 1931 Seth Thomas catalog shows this clock, with a retail price of $12.50. I think the dial is aluminum with printed numerals (even though the catalog says silver-plated, that may have been an earlier version).

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Repair job 8691. The No. 89 is an efficient movement that can use thinner mainsprings than are usually supplied with it. When I received the clock for repair, the time mainspring was 3/4 by 0.0187″, too strong and not original. The strike mainspring was 3/4 by 0.0165″ but had a squeaky action after cleaning and lubricating (this squeaky action, in my experience, means the spring may fail soon). I replaced both mainsprings with MS298 11/16 by 0.015 by 108″ springs.

I burnished or polished the pivots and installed 14 bushings. I tightened the click rivets, opened the pallets slightly and adjusted the depth. The mainwheel teeth have little wear, 5% or less.

The cleaning solution I use now is Magic Cast from Timesavers. It was made for years under the name Historic Timekeepers, and I used it from 1995 until it was discontinued several years ago. For very dirty clocks I will pre-clean the parts in a different batch of solution, and save the good cleaner for final cleaning or clocks that aren’t super dirty.

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  1. I have this clock and I want to repair it for my father. He purchased it from an estate sale in the 1960s. It keeps perfect time but doesn’t chime. Is this and expensive repair? How much should I expect to pay? The last service/cleaning was 10/2005.

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