Adjusting a 1924 Elgin 315 12s Pocket Watch to 5 Positions

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Nothing brings people together like being stuck in a boring committee at work. And when people are brought together, in my experience, they inevitably end up talking about old watches. I don’t how that happens, but you probably have the same experience.


Anyhow, a pal at work mentioned that she had an old, broken pocket watch that belonged to her grandfather, and that she had hoped to one day pass it along to her son. Broken heirloom pocket watches are my specialty, so I was happy to take it look at it.

And here it is, a neglected but charming Elgin. This is a 12-size, grade 315 watch with 15 jewels. According to the incomparable Pocket Watch Database, this watch dates to around 1924.

Right away, you can tell that this one will need some attention. The watch apparently hasn’t had a crystal in decades, and it is grimy and stuffed with white fibers. It isn’t running, either.

A watch without a crystal is a magnet for gunk. And this watch has some funky gunk. Here’s the view beneath the dial.


This cannon pinion looks like it was lubricated with tree sap and fungus spores.


The watch has two main faults. The balance staff is broken, as I suspected.


And the center wheel is damaged. One of the teeth looks like it got into a bout of fisticuffs. Perhaps a mainspring broke and the safety pinion didn’t disengage?


Repairing the Patient

After the watch got a good scouring and a new white alloy mainspring (it takes an Elgin part 2339 mainspring, if you’re working on a grade 315), it was time to repair it. I had a parts watch with a 315-compatible center wheel, so the wheel was swapped instead of repaired.

For the balance staff, this watch takes an Elgin part #2802 staff. Like most old staffs, it comes in a range of pivot sizes, so the first task is to measure the size of the current staff. You can either measure the size of the staff or measure the size of the jewel holes.


My handy pivot gauge showed that the current pivot fit easily into a .12 mm hole and almost into a .11 mm hole. The staffs are available in .09 and .10 diameters, so I went with a .10 pivot staff.

I’ll post a how-to guide to replacing balance staffs someday. (In the meantime, Mark Lovick has a great video post on it.) This staff required punches 17A and 17B in my Marshall staking set.

In Science of Watch Repairing Simplified, A. Gideon Thisell describes running a watch in “half time” (Chapter 13, p. 63). Basically, you insert the balance wheel without the hairspring, wind the watch, and let it run. The pallet will give an impulse to the jewel, thus flicking the wheel. The jewel should hit the other side of the pallet fork, swing back around, and enter the fork with enough force to unlock it. If the watch is set up well, it will run in all 6 positions without the hairspring. If it doesn’t tick, it is much easier to find the escapement fault without the hairspring.

When it was finally assembled, this watch ticked spectacularly from the start. It ran fairly fast, but the amplitude was great, the rates were pretty stable, and the beat error was under 1 ms.


After running a few days for the mainspring and oils to bed in, this watch will be ready for fine-tuning.

Adjusting the Watch

As always, it helps to consider the good omens and bad omens when evaluating a watch for adjustment. This watch has some good signs:

  • Elgin made solid watches, and this little fellow is clean and running nicely.
  • The rates are stable.
  • The balance wheel looks like it hasn’t been fiddled with.

And, of course, there are some bad signs:

  • This watch lacks mean-time screws, which make fine adjusting much easier.
  • It’s a 15 jewel watch, the minimum for a solid pocket watch. But by 1924, when this watch was made, 17 jewels was the new 15.

I’m going to aim for reasonably good time in 5 positions. For a pocket watch, that’s all positions except pendant down (PD). Because this is an “heirloom watch,” I’m going to adjust it without removing weight from the balance wheel. By only adding weight, all the adjustments are reversible should someone later wish to undo them. But fine-tuning is very hard without removing weight, so we’ll by necessity apply a looser accuracy standard for this watch.

As always, we start by measuring the rates at full wind (actually around 90% of full wind, as we explained elsewhere). This watch is fast and furious:


But adjusting this shouldn’t be hard.

  • The amplitude is great in all 6 positions.
  • The dial up (DU) and dial down (DD) positions are essentially the same, and that’s the first step in adjusting. Getting DU and DD aligned can be vexing, so it’s nice when they are tight.

The next step is finding the heavy spot on the balance wheel. As we have shown in the series of posts on “Dynamic Poising,” we start by measuring the vertical rates at low amplitude. The goal is to find the fastest position. In that position, the heavy spot is below the balance staff.

Here are the vertical rates at low amplitude. The watch is fastest at the diagonal between PU and PR. (Keep in mind that pendant right and left are defined from the dial side, but we’re viewing the watch from the movement side, so PR and PL are reversed.)


The watch is fastest in this position.


On the balance wheel, the heavy area (shown in red) is awkwardly between two timing screws. The light spot (in green) is opposite it.

So, what do we do? Readers of this blog know that we need to make sure the horizontal and vertical rates align. If the watch is running fast, then we add weight. This makes the vertical positions more similar to each other and slows the watch down. All the rates will thus converge. As we’ve said before: if fast, add weight to the light spot; if slow, remove weight from the heavy spot.

Time to tap into the stash of timing washers.


I placed a washer from Bottle 5 under each of the two screws.

Adjusting is a rinse-and-repeat affair. Adding those two weights greatly improved the timing, but another round was needed. After adding another small washer, here’s what we were looking at:


This is pretty good. The rates are very close in the 3 main positions (DU, DD, PU) and not bad overall.

After nudging the regulator so that the watch runs around +3 seconds fast DU/DD, we’ll call it a day, but with a wistful sense of what might have been.

This watch is capable of much closer rates. If we would remove weight, it would be easy to nail down all 6 positions, just like we did for some 12-size Hamilton and Illinois watches. The wheel is just a bit out of poise, but such small errors are handled by removing a miniscule amount of weight. Pocket watch timing washers aren’t teeny-tiny enough to even it out.

That’s the trade-off you make when you adjust without removing weight. The adjustments are reversible and the watch’s originality is maintained, but the timing usually won’t be as close.

Cleaning the Case

Finally, we turn our attention to the case, which has the grime of ages on it. The case got some quality time with a toothbrush and dish soap, a round in the cleaning machine, and a light buffing with a Menzerna P175 yellow compound, which shines up the gold without removing material.

This is a sharp case: 14K gold-filled and nicely decorated.


The GS PKH crystals are good replacements for pocket watches. Glass crystals have more historic appeal, but plastic crystals are plentiful, tougher, and easy to buff clean if scuffed.


The watch is cased and keeping great time. All that remains is to attach the bow. Now where are those confounded bow-opening pliers when you need them…

Wrapping Up

All’s well that ends well. This little watch is ticking away merrily. The toned dial and hands show the watch’s years, but I hope I’m looking this good when I’m 92 years old.