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Tightening a Solid Cannon Pinion

This is the dial side of a Waltham 1857 model pocketwatch movement. These have a solid, thick walled, cannon pinion.

The cannon pinion is friction fit on the center post and intended to grip the center post tight enough so that the pinion (and thus the hands) turn with the post while the watch is running. But the pinion slips too, so as to allow setting the watch.

A common problem is that the cannon pinion slips too easily, and so slips when the watch is running. As a result, the hands do not move, even though the watch is ticking away normally, and the center shaft is turning. To correct this, the grip of the cannon pinion has to be tightened. Later watches have a sort of finger cut out in the side of this part. This finger can be bent inward to grip the center shaft more. But earlier watches like this one have a thick, solid cannon pinion.

In these instances there is no good fix. The cannon pinion can not be safely crimped as it will break - or damage the tool used.

From time to time, I see one like this one.  A portion of the part's side wall has been filed away, very close to breaking through to the hollow inside, but not quite. Then the inside of the cut out is dimpled in, as so tightens the cannon pinion's grip.

It's not a great fix, but some cases there are no good options. At least this is a neat and tidy job.


As an aside, the teeth at the base of the cannon pinion drive the minute wheel, which in turn drives the hour wheel. This "dial side works" is not shown here, but it hard-ties the two hands to each other. One can not move with out the other moving, and they are an independent part of the train except as driven by the center wheel, which turns once around in 60 seconds.

Also note the squared top of the cannon pinion on this watch, for manual setting from the front with a watch key.


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