Adjusting a Mishandled Hamilton 4992B 16s WWII Military Pocket Watch

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When the word gets out that you can fix a grandfather’s old watch, some interesting watches come out of the cabinets and sock drawers. My friend with the charming 18-size Elgin mentioned he had another watch, but “something plain, not anything so cool or fancy” as the Elgin.

So I was surprised to learn that he was talking about this watch.

Yes, indeed—a military-spec Hamilton 4992B made during World War II.

The 4992B is a military-spec watch based off the popular 992B. It has a some great modifications:

  • a sweep second hand with a jeweled bridge as a pinion bearing, not some cheap spring as in many other watches
  • a hacking lever to stop the balance wheel, which allows accurate time setting
  • a 24-hour dial in which the hour hand travels only once around the dial each day.

These are phenomenal watches, possibly the nicest pocket watches made by an American company. Hamilton adjusted them to 6 positions, and they have all the features one would want in a high-grade pocket watch: micrometer regulator, mean-time screws, alloy hairspring, and the like. I was excited to work on it and expected great results.

But when I stripped the watch down, some surprising flaws popped out. A bad, bad man once worked on this fine watch.

This watch’s timing screws had been deeply gouged.

This is rough and ugly dimpling. We’ve condemned this approach to removing weight in earlier posts. Dimpling the screw face is a move for desperados and miscreants—especially solid gold screws on a high-grade Hamilton.

Don’t hack away at solid gold screws, people. Here’s a close-up:

That hurts.

Beyond that, someone changed the balance staff at one point in the worst way. When you change a staff, it is good to remember where the roller and hairspring stud were located. You want to replace the roller in the same spot so that the wheel resembles its factory poise.

You could use a fine-tipped marker, for example, because the ink easily washes off in denatured alcohol or cleaning machine solutions.

Or you could gouge the balance wheel with screwdrivers. Note the scratches on the wheel to mark the roller jewel position.

Even worse was the marking of the hairspring stud with an arrow scratched into the arm. Finally, look at the hairspring collet—it has been a bit smashed, like it was staked on off-center.

Cleaning and Adjusting

As always, the watch got a good cleaning, oiling, and demagnetizing. I let it run for a few days to settle in and then got down to adjusting.

The baseline rates weren’t terrible, but there was some good and bad news.

On the good side, the dial up and dial down positions were the same. In Kleinlein’s approach to adjusting, aligning the DU and DD positions is the first step. Those positions are often a hassle if they vary.

But on the bad side, the horizontal rates (DU and DD) are much slower than the vertical rates (PU, PR, PD, and PL). Ouch.

We haven’t talked much about such problems much in this blog. Sometimes called hanging/lying differences, these disparities can be tricky to troubleshoot and correct. You can end up with a watch where the DU and DD agree with each other, and the 4 vertical positions agree with each other, but the average horizontal and average vertical rates disagree.

I had feared this when servicing the watch because lopping off too much weight can cause the lying positions to diverge from the hanging ones. Between its gold screws and the collet, this watch has shed a lot of weight from its balance assembly.

I’ll start some posts on hanging/lying differences soon: there are many causes with many solutions. For this watch, I’m not willing to do what needs to be done (ideally, replacing the dimpled screws). This isn’t my watch, and I’m reluctant to modify heirloom watches too much.

Instead, I did a few rounds of dynamic poising, adding weight each time. This will improve all the rates, but you can’t add enough timing washers to make up for all the lost weight.

I called it quits here: good enough for a daily carry if my friend wants to take it to work, but not as good as a 4992B in good condition is capable of.

The Dial and Case

The dial is a painted 24-hour dial. I’m always reluctant to touch or clean old painted dials, especially this one.

It looks like it has been touched up in the past, so the paint is probably fragile.

The case is plated base metal, so it will get a good scrubbing with a soft toothbrush and soap. Otherwise, these cases can’t be polished without a risk of stripping off the plating.

This watch came with a rubber holder.

It has a countersunk hole so it can be screwed into a wall or console. The watch fits in it snugly, and the cut-out allows the pendant to be wound and set.

The watch had a plastic crystal that my friend wanted to keep, so it got a thorough buffing to polish out the nicks and scuff.

By the end, the watch was looking ready to be pressed back into service.

Wrapping Up

Working on this watch was a bit disappointing. I had high hopes for its accuracy. It didn’t turn out terribly, but it is shame to know that the watch would be capable of much better.

This watch has, however, motivated me to finally get some posts up about adjusting for vertical/horizontal differences, so stay tuned.