Mainsprings for Seth Thomas No. 89 Movements

September 10, 2007 | By | Reply More

So far, the .0155 inch to .0158 inch thick mainspring has been perfect for the time train. For the strike train, it is satisfactory, but the striking speed may be too slow to suit some people. On a ST “Giant No. 1” oak shelf clock I am currently repairing, I am going to try an (approximately) .0165 inch thick spring, as the customer does not want the striking to be too slow. (At this moment, a .0155 inch thick Merritt’s spring is on the strike side, and it IS strong enough to power the strike for at least 9 days, but the striking sounds slow.)

I’ll post again when this job is complete.

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Category: American Clock Mainsprings

Last updated: November 28, 2009

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