Adjusting a 1926 Two-Tone Illinois 89 18s Pocket Watch to 6 Positions

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I didn’t intend for this blog to be an homage to all things Illinois, but it has happened. Here’s another Illinois pocket watch—the last for a few posts, I swear.

This is a quirky watch: an 18-size pocket watch, Grade 89, from 1926. Illinois made these Model 6 18-size watches for a long, long time. The Illinois 69 in an earlier post, for example, was made in 1913, and it’s the same model.

I wonder what shoppers in 1926 thought of this watch. As a full-plate pocket watch, it looks pretty much like the Illinois watches dating to the 1880s. In 1926, 12-size and 16-size watches were the hot thing in pocket watches, and the shift to wrist watches was underway. Not many companies still made 18-size watches. For its time, the technology in this watch is dated: a full plate design with a single roller would seem dowdy next to the motor barrels, double-rollers, and bridge-plate designs that were popular in the 1920s.

Perhaps it was pitched as a retro timepiece, a throwback for the vintage fans? Is this the watch that the 1920s version of hipster vinyl fanboys bought? Retro or not, the two-tone pattern with matching gold-plated screws and hardware is a cool design.

Anyhow, this watch wasn’t working when I bought it. The balance wheel wiggled, so I suspected a broken balance staff. The watch got taken apart and cleaned.

These old pocket watches have been through many, many hands, so they usually have a few bugaboos. This one had an ugly roller table.

The table is shellacked to the balance staff. I imagine that the balance staff was replaced and the hole in the roller table was too big, so someone shellacked the table to the staff as a quick and dirty fix. That’s not good, but I’ll leave it alone.

It’s hard to show in a  picture, but the roller jewel is too small. It looks much smaller than the typical single-roller 18-size jewel, and it doesn’t contact the pallet fork along the fork’s full depth. That’s a bad sign for good amplitude and precise timing. The “contact patch” (as tire guys say) between the roller jewel and pallet is smaller if the jewel isn’t deep enough.

And someone—I suspect the roller-table shellacker—adjusted the balance wheel’s endshake with a dial washer. Notice the thick steel washer folded in half. When placed near the rim (between the screw and the edge), a washer like this will cause the balance cock to tilt toward the plate, thus reducing endshake. If placed between the screw and the wheel, you’ll the get opposite effect.

At least a dial washer is a better fix than chiseling “pigs ears” into the bridge.

But the good news was that the balance staff wasn’t broken—the jewels were just too small. The watch wouldn’t tick dial-up because the jewel hole was too small for the pivot. A new jewel did the trick.

The watch got a trip to the spa, a new alloy mainspring, and a stint on the demagnetizer. After it ran for a few days, it was time to adjust the watch to positions.

Adjusting the Watch

Before adjusting, it’s good to think through the watch’s pros and cons so you can set a realistic goal for adjusting. Some watches can’t or shouldn’t be adjusted; others are capable are loose timing standards; and some, like our recent 21-jewel Waltham, can be adjusted to run better than they did when they left the factory.

The good omens:

  • Illinois made great watches. A 17-jewel watch from the 1920s should be capable of keeping good time across positions.

The bad omens:

  • The watch has escapement issues. An undersized roller jewel gives less contact surface with the pallet fork. It won’t strike or be flung as cleanly as a larger jewel, so amplitude will suffer. We’d expect dial-up/dial-down differences because the roller jewel will fit deeper in the pallet fork in one position than the other.
  • One of the mean-time screws is seized, so they can’t be moved to modify the rates.

All told, we’ll aim for 10 or so seconds from zero in all 6 positions: pretty good, but not as tight as a railroad-grade watch from this era.

Dynamic Poising

Here are the baseline rates. (Earlier posts explain the abbreviations, if you’re just joining us.)

Not too bad—we’ve seen much worse on this blog.

First, it is running fast, so we can adjust it by adding weight—an easier method than removing weight for big changes.

Second, the dial up (DU) and dial down (DD) rates are close enough. Aligning DU and DD is the first step, and it can be the most painful part of adjusting. The disparity is probably due to the undersized roller jewel, which gets a better strike in one position than the other.

But the amplitude isn’t great. It’s good enough—around 285 horizontal, 240 vertical—but we’d expect better (at least 300 horizontal). I suspect the undersized roller jewel is the cause.

Next, we need to find the heavy spot. The vertical rates differ because one part of the wheel is heavier than another. This is where dynamic poising comes in. Instead of spinning the wheel around a quaint poising tool, we let the watch run at a low amplitude (around 140-160 degrees) on the timing machine. If you do this in all 8 positions, you’ll find that one position is faster than the others. The heavy spot is directly below the balance staff.

For example, when this watch was run at low amplitude, it was fastest in this position. It is in between pendant up (PU) and pendant right (PR, defined from the dial side).

This means that the heavy spot is where the red circle is. Basically, either that screw is a little too heavy, or the screw directly opposite it is a little too light.

So, we could make the heavy screw lighter by removing weight—but that would make the watch run even faster. The DU/DD positions would start to diverge from the vertical ones.

If we made the light screw (under the green circle) heavier, that would make the watch run slower. That’s the right call. Remember, if fast DU/DD, add weight; if slow, remove weight.

So we begin the rinse-and-repeat process of adjusting. I added a big timing washer under the light screw, but the rates were still far apart. The heavy spot was in the same place, so I added another washer to the screw next to the light spot. But this wasn’t a big enough change, and the heavy spot was still in the same place. After three rounds of adding washers to the same two screws, the rates looked great.

After slightly moving the regulator to bring the watch to time, we ended up here:

This is better than I deserved, given the grade and condition of the watch. The rates are all within 10 seconds of zero and pretty close overall.

As expected, there’s a DU/DD difference that probably reflects the small roller jewel. And the amplitude is fine but not great.

The Dial and Case

Like our Illinois 69, the Illinois 89 came in a nickel swing-out case. These cases are easy to polish to a striking shine. The case had a plastic crystal, but this watch would be more dignified with a glass one. After some cleaning and polishing, here’s the fellow in fine form.

Wrapping Up

Overall, all’s well that ends well. The watch turned out better than it should, given the tacky roller and undersized jewel. I’m tempted to take the watch apart, replace the roller jewel, and see if the amplitude cranks up, but there are many (non-Illinois) watches that need attention.