Lesson learned - Running American pocket watches uncased

[mbwatch]

I'm not sure I have any question left here, but want to relate my Captain Ahab story getting this junk Elgin grade 206 7j watch to run. It came to me in a bag of broken watches a relative's acquaintance handed over. The "before" picture hides the fact that all 3 brass wheels were seized together with green corrosion. The case was black, but this I learned right away was just a badly tarnished coin silver. It cleaned up really nicely. It's a type of case I have not encountered before, extending a 6 size movement to more like the a 16 size case with a broad spacer ring.

When disassembling the case, I broke the stem sleeve. It was rusted and brittle. I figured this was unimportant and I would eventually replace it. Though I was surprised to find how much those parts sell for. I expected them to be available by the sackful, but instead sellers want $15-$20 for a single one. I kicked this down the road so I could get the movement to run.

The movement cleaned up okay, and I was able to remove corrosion enough to reuse all but the 4th wheel. It had 5 or 6 teeth that were eaten away not enough to stop the watch, but to send its timekeeping haywire every 45 seconds. I worked on this over several months, replaced some wheels with spares, tuned the escapement to my current skillset. The movement ran, eventually acceptably well. The balance is out of poise I think, based on a 40sec positional delta. I can deal with that when I have a poising tool.

But with the dial and hands installed, it would never keep accurate time. Sometimes it would be good for a day then suddenly lose ten minutes or lose 6 hours. It felt like a cannon pinion problem. I got the tools to tighten the cannon pinion. This didn't help at all. I replaced the center wheel because its arbor was kind of worn. That did not help either. I replaced the cannon pinion entirely with a donor's. It had a positive snap on install and good feel to handsetting but still no change in behavior. I thought maybe the hour wheel was riding up out of mesh with the minute wheel so I tried manipulating and eventually stacking dial washers, no change. I learned how to close the holes in the hands for a firmer fit on the hour wheel & cannon pinion.

I was going to give up on this one when I found someone selling a bag full of stem sleeves for a reasonable amount. I bought them and installed one that fit, planning to sell this watch on and note its fault for someone else to figure out. But after installing that stem sleeve and recasing it, the watch is now keeping time all week without any issues in the motion works.

Why?

Because the keyless works on this type of watch are inverted. The stem must be pushed in and secured by its detent with a stem sleeve to engage the winding mode. Otherwise, its default position under spring tension is to engage the hand setting wheels (in the photo above, that spring is not engaged but that's not the problem). All the while I was trying to get the hands to keep time, it was running uncased and the cannon pinion was therefore driving all the handsetting wheels. It can't do that without slipping occasionally and that was its issue all along. It still isn't perfect, I need to troubleshoot a problem with the spring tension in the keyless works while it actually is engaged in winding mode.

But now it's all together, and will make a nice little desk clock or something once I clean up the dial a bit to hide those cracks. And the next time I work on an American stem wind/stem set watch I will make sure it is cased when I test it out with dial & hands.

[mewherman]

You can clean the dial in denture cleaner to reduce the appearance of the cracks.