Waltham 1883 Model

Here we have the center wheel from a large, 18 size, Waltham pocketwatch. This is a fairly large part, right in the middle. It drives the minute hand.

This watch has a "safety pinion". The pinion on the center wheel, which is directly engaged with the mainspring barrel, is threaded on to the shaft. In fact, the threads are left-handed, meaning they turn the opposite direction from usual. This protects the rest of the train if the click gives way, or the mainspring breaks, causing a sudden, powerful, force to transmit down the gears in the opposite rotation from normal. This opposite force will turn the pinion on these reverse threads causing it to rise up the shaft until it move out of the way and disengages from the mainspring barrel, thus cutting off the power.

Clever...

In this case, it has at some point "fired" but there was such force that it has jammed at an angle and wedged itself on the shaft. So far I have been unable to budge it. In addition, one of the pivots on the next gear down the train, the third wheel, is broken so probably some amount of force got through. Usually it's the escapement that gets damaged.

This watch is lever-set. Here are the various parts that live under the dial.

Here are those parts installed.

This is a tool for squeezing the hairspring collet tighter. I changed the balance staff on this movement and the hairspring was too loose on the new staff.

This tool has a limited range though. If the collet is too loose, it has to be changed.

This 18 size Waltham is an old one, and a fairly rare model. It was made about 1887.

I had quite a bit of trouble with the mainspring on this one. It wants to come unhooked from the center arbor. Although the arbor really does look OK, I finally jut replaced it with one that I altered a little in the lathe. The replacement has a large hook. I think the spring that this watch takes (at least according to the documentation) is very strong. A weaker spring would likely be just fine.

See more about the American Waltham Watch Company, and the watches, here!