Big Ben balance spring installation

by Graham
(MA)

On Big Ben #5 Chime Alarm, when installing a new balance spring, must it be set so that the small pin that engages the small fork on the anchor be set so that it is left pointing right at the center of that small fork that it will be engaging with?

Reply: Hi Graham, I'm not sure I follow exactly what you are asking. But, when you install a new hairspring, run the free end through the regulating mechanism (F-S lever) then insert it into the anchor. The pin then is inserted from the outside and holds the spring in place. It should be in the center of the fork.

The spring may need to be adjusted several times until you get the spring the correct length to keep accurate time with the regulator (F-S) in the approximate center of its travel area.

If this is not what you need to know, please comment here with more specifics and I'll try to answer. Bill