safety pinion-A pinion in the center wheel designed to unscrew if the mainspring breaks. My question is,after the mainspring is replaced,how is the pinion re-set on the center wheel.Always willing to learn.

Frank Juchniewicz

Frank,
Usually the safety pinion gear is screwed onto the center wheel arbor using a left handed thread. When the mainspring is tightened, this tends to tighten the pinion gear onto the arbor. But, when the mainspring breaks, the power transmission reverses, and the pinion gear is quickly unscrewed from the arbor, thus saving the gear train from damage.
So, after the mainspring is replaced, all that has to be done is to screw the pinion gear back onto the arbor, remembering that, since the threads are left handed, the pinion is screwed on counter clock wise, or if you are in the UK, anti clock wise

BTW, Most (but not all) of the screws used to hold the crown wheel in place are also left handed, for the same reason, to keep them tight when winding.

Ed Ueberall
NAWCC #49688
IHC #34

Thanks guys, the reason I asked was I got hold of an Elgin 16s,7j,grade 290,model 6
I found the mainspring had broken and the center wheel pinion was loose on the arbor.

Frank Juchniewicz

Frank,

Just to add a little to the great responses posted so far on this discussion, is a slide that represents an Elgin 16s Center Wheel (aka 2nd Wheel).

Anytime you replace a broken mainspring, always remove the center wheel assembly and check for proper alignment of the arbor, wheel and pinion. Sometimes the pinion does not totally unscrew from the arbor and during winding it will retighten the pinion. If the arbor is not properly seated in the wheel recess, the wheel will wobble. The watch may run until the tilted part of the wheel comes in contact with the plates or other components.

After taking a movement down, I usually check all train wheel assemblies in my lathe to ensure they run true. This can also be done in the movement prior to installation of the pallet lever. Wind the watch slightly and check each wheel for wobbling or binding. This is easily accomplished on a 3/4 plate movement. For a full plate movement the wheels should be checked using your lathe or a pin vice prior to assembly.

John D. Duvall
NAWCC Member 144772
NAWCC IHC Happy Camper 192
Chapter 185 Watch Repair Moderator

Thanks John.
For the very helpful tip,and illustration. I will certainly remember it when I go to tackle the mainspring job.

Frank Juchniewicz