Seth Thomas Adamantine

As received: the time mainspring was 3/4 inch wide by 0.0175 inch thick, and the strike mainspring was 0.0165 inch thick. There was very bad T4F pivot hole wear. The strike train had virtually no wear.

Showing front time pivot holes 3, 4, and 5 before bushing. Note excessive wear on #4

After the overhaul, (I did no bushings on the strike side), the pendulum motion was excessive, and the striking sounded sluggish. I swapped the time and strike mainsprings, and then the pendulum motion was excellent (could still have been less) and the strike sounded fine. Here are the final values of the mainspring sizes (remember that these are ORIGINAL OLD mainsprings, if they were being replaced, thinner spring should be used):

Time Spring: Original old 3/4 x 0.0165 inch

Strike Spring: Original old 3/4 x 0.0175 inch

The bottom of the clock showing date code “6091L” which means December 1906.

My job no. 4487

Share this post:



  1. I have a white Seth Thomas Adamantine Dec. 1906 11 jewels 6 size I’m looking to seel to someone who is very interested

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.