Seth Thomas Tambour Mantel Clock, Adamantine Finish and Bim-Bam Strike

This Seth Thomas mantel clock from about 1910 – 1920 has an Adamantine (celluloid) wood-grain finish. The movement is marked “89” and has bim-bam striking on the hour and a single tone strike (the high note only) on the half-hour. The case is 19 7/8  inches wide and 9 1/2 inches tall. The dial is silvered brass with printed numerals and a 4 7/16 inch diameter minute track. The minute hand is 2 3/8 inches long.

I cleaned the movement, polished the pivots, and installed 13 bushings. The pendulum rod and pendulum bob were previous replacements. The clock was losing time, so I shortened the pendulum rod by 3/8 inch.

I replaced the time mainspring because it was causing wear to the mainwheel teeth. I intended to keep the original strike mainspring, but it broke after cleaning and lubrication, as I was winding it into the clamp for re-assembly. The original mainsprings have the following measurements:

Time: 3/4 wide by 0.0185 inch thick (thicker than usual for a Seth Thomas No. 89 movement)

Strike: 3/4 inch by  0.017 to 0.0172 inch thick).

The replacement mainsprings are no. 280-19-003 from Colonial Clock Co., and have the following measurements:

Time: 3/4 inch wide by 0.0158 – 0.016 inch thick by 120 inches long

Strike: 3/4 inch wide by 0.0162 inch thick by 120 inches long.

The movement is a variation on the basic No. 89 having bim-bam strike. It was made before Seth Thomas started giving different model number to variations on the basic movement.

Here is a video showing the pendulum motion and the striking:

See more photos.

Repair job 5640.


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  1. The easiest way is to grasp the HOUR hand near the center, and rotate it to point to the hour that the clock is striking. Then use the MINUTE hand to set the clock to the correct time, moving it forward.

  2. Hello,
    I have a Seth Thomas #7 Sentinel mantel clock and it chimes one too many times on the hour. Can you tell me how I can adjust this?
    Thank you,

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