Roller and Beat

Here is the roller being installed on the new staff using stakes designed for this purpose. This watch has a two-piece double roller.

The hairspring presses on the assembly, on the opposite side from the roller, friction fit.

The spring's orientation is important. The stud at the outer end of the spring is held by the balance cock, which also has the upper balance jewel in which the balance wheel turns. The spring has to be turned on the staff so that the stud falls such that when at rest, in the middle of its to and fro motion, the roller jewel falls exactly midway in the middle of the pallet fork (on a line joining the balance jewel and the pallet fork jewel).

This is so the balance wheel will rotate an equal amount to the left and to the right as the watch runs. If this set up is not correct, the watch is said to be "out of beat". If it's off enough, the irregularity in the "tick-tick" cycle is audible even to the untrained ear. The balance turning too far one way or the other wastes power, causes unstable time keeping, and can stop the watch.

Here the balance assembly is in place. The hairspring stud is fixed with a set screw at the outer, narrow, end of the balance cock.

This movement is a grade 455 Elgin, 16 size, 19 jewels, made about 1920.