Adjusting a Hopeless 1922 Illinois 406 12s “Parts Watch” to 6 Positions

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Our last example watch, the 1923 Illinois Bunn Special, was way too easy to adjust, so I thought I’d dip into the pile and try adjusting something more challenging.

Enter our current patient: a 1922 Illinois 406, a 12-size pocket watch with 19 jewels. It’s basically like the Illinois 405 we adjusted┬álast month, but it has 2 more jewels.

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I picked this watch up as a parts watch. The seller honestly noted that it was in bad shape—it wouldn’t tick, and the balance staff was probably broken. I thought the case alone was worth the money—it look like it would clean up well, and it had a nice glass crystal—so I bought it and stashed it with my parts watches.

Let’s see if we can revive this little guy.

Evaluating Our Prospects

Just as our Bunn Special was pristine, this Illinois 406 was in rough shape. As always, we start by forecasting how easy or hard this might be.

The good omens:

  • Aside from the high quality of Illinois watches from this period, there are no good omens. This looks like a parts watch that was fiddled with by some inept hands.

The bad omens, in contrast, are legion. The balance staff wasn’t broken, but most everything else in the escapement was wrong:

  • the roller jewel was loose and set far too deep, so it scraped against the pallet guard pin
  • the hairspring regulator pins weren’t parallel
  • all the balance jewels were wrong. The dial-side jewel was a simple plate jewel loosely pressed into the hole. The upper jewel was the right diameter but the wrong depth.
  • the balance wheel and roller are a golden color. At first I thought they were gold plated, like the screws, but this looks like the straw color achieved through low-heat tempering. (A mishap related to the poorly-set roller jewel, perhaps?)
  • the pallet’s guard pin was a bit too long, so it scraped the roller
  • a couple of screws were missing
  • the mainspring barrel cap was warped, causing the barrel to bind against the arbor

I happened to have the jewels and screws from another parts watch, and repairing the roller jewel, barrel, and pins was straightforward. The watch got a good cleaning, jewel scrubbing, oiling, and demagnetizing, along with a new white alloy mainspring. I then set it in beat (to around .3 ms) and left it to run for a day.

The amplitude was excellent (at least 260 vertical and 290 horizontal), and the rates were clean and stable.

Getting Started

Illinois-406-T0I set the regulator to the middle of the fast/slow index, fully wound the watch, and measured its rates in all 6 positions. How did it look?

Not bad, actually. First, the dial up (DU) and dial down (DD) rates are close, and that’s the first essential step in positional adjustment.

Second, all the rates are reasonably close. This watch has had a bad life, but the wheel’s poise is pretty good—all the vertical rates are fairly similar. (Keep in mind that pendant left (PL) and right (PR) are defined from the dial side, but we’re working on the movement side, so they are reversed.)

Illinois-406-LowWe then use dynamic poising to identify and correct the heavy spot in the balance wheel. As we’ve explained in detail elsewhere, heavy spots have bigger effects at low amplitudes. We can thus pinpoint the heavy spot by measuring the rates at a low amplitude, around 140 degrees.

The chart shows the fastest rate in red. The heavy spot is directly below the balance staff when the wheel is in this position. Naturally, the lightest spot is opposite it, in green. This watch ran fastest when pendant up (PU), so the spot below the balance staff when the watch is PU is the heavy spot.

To fix a heavy spot, we either add weight to the light spot or remove weight from the heavy spot. Because this watch runs fast DU/DD, we would add weight. Adding weight to the light spot will improve poise (making the vertical rates more similar to each other) and slow down the watch (making the horizontal rates more similar to the vertical ones).

I broke out my stash of timing washers and placed a small one—rated for 1 minute for a 0-3/0 watch—under a screw at the light spot.

The Next Rounds

And so it begins again. After making an adjustment, we wind up the watch, measure the rates, and see if what we did was enough. Fine adjusting will usually take a few rounds. For the first 2 rounds, I added weight with timing washers. For the 3rd round, a mean-time screw on the balance arm was the heavy spot, so I slightly unscrewed it. And for the next couple rounds, I lightly removed weight from a screw using a balance screw undercutter and escapement files.

Wrapping Up

Illinois-406-FinalAnd where did we end up? Here are the final rates. These are excellent by any measure. The rates are close together, and the biggest difference (PR and PL) is only 8 seconds. The most important pocket watch positions—DD, DU, and PU—are only a few seconds apart.

As an aside, I like to set my watches a bit fast. As Kleinlein points out, most watches will lose a couple seconds a day in use—the so-called “personal error.”

I’m glad I salvaged this little watch. The case and glass crystal look great, the dial has a nice aged look, and the movement runs incredibly well.

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But if you’re just learning watch adjustment, I wouldn’t recommend using picked-over parts watches. They’re cheap for a reason.