Mainsprings for Sessions Black Mantel Clock

October 22, 2009 | By | Reply More

I recently overhauled this Sessions black mantel clock from around 1903 – 1910. It was a routine overhaul including polishing the pivots and installing bushings. A previous repairer had installed two screw-in bushings (a no-no!). I replaced these with KWM size 4 American bushings. The mainwheels were made with Gilbert-style clicks, which are more robust then the standard Sessions clicks.

The original mainsprings seemed too strong. The time spring was 0.0182 inch thick, and the strike spring was 0.0178 inch thick. I replaced both with thinner mainsprings, Merritt’s Antiques P-1956, 0.0165 inch thick, to reduce future wear to the mainwheel teeth. The escapement takes an excellent motion.

Repair job 4949.

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Category: American Clock Mainsprings

Last updated: August 31, 2011

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