Parenthood is a solemn responsibility. The kids are always listening, and I think I can admit that I’m not always a good role model.
For example, while visiting a local coin shop with my 7-year-old son, I saw a broken Waltham 1908 7-jewel pocket watch—and I bought it. My son, being of an impressionable age, got excited by the idea of repairing it. He has some respectable watchmaking skills for a second grader, so I thought that this watch, if nothing else, would be a fun project we could tackle together.
But some principles shouldn’t be violated—don’t bother with the hassle of 7-jewel watches. They are the road to vexation and madness, as this post proves.
What’s Wrong With 7 Jewels?
Seven jewel watches were budget options in their day. They weren’t designed to keep excellent time, so they usually lack features that make adjusting easy. Our Waltham, for example, lacks mean-time screws and a micrometer regulator.
In addition, the cheapness of 7-jewel watches made people under-appreciate them. Fine watches tend to survive the years in better shape than crappy watches because the owners took better care of them. Valuable things get better treatment: more frequent repair and service, gentler handling, and cleaner storage.
And finally, jewels act as bearings for the hard steel pivots. Without jewels, the pivots simply sit in metal holes. The metal-on-metal contact, over the years, grinds away the hole into an oval shape. The gear no longer spins upright, and it will eventually fail to engage with the other gears, causing the watch to stop.
Here’s the upper 4th wheel hole, for example. It is starting to get a bit oval in shape.
Repairing the Patient
This watch is a Model 1908, Grade 610 from 1907. It has a motor barrel, but unlike the sweet 21-jeweled version with a jeweled motor barrel from a prior post, this one has a humble motor barrel. The barrel has a single-piece arbor instead of a the two-piece threaded arbor found in nicer models.
The watch got stripped down, evaluated for bugaboos, and then cleaned. So much was wrong with this watch.
The balance staff was broken, but this watch uses friction-fit staffs. These are quick and easy to replace, so we staked in a new one. My son is a staking set ninja.
The escapement was beyond wrong. The roller table scraped against the pallet’s guard pin, which had been bent too far forward.
The pallet fork had a chipped tooth.
The banking pins were bent. Who knows why—they’re controlled easily with screws and don’t need to be physically bent.
The roller jewel was missing, so someone crafted a rough steel pin and fit it loosely it in the hole.
And to make matters worse, that guy roughly filed the pallet horns to “fit” the width of the new pin.
By this point, I had a sinking feeling of dread. This watch should be abandoned for parts, but my son wanted to fix up the watch and wear it to school, so it was time to get into the nitty gritty.
We reformed the pallet fork’s pin and the banking pins, and we fastened the steel pin to the roller table with shellac to keep it tight and stable.
The watch got a new mainspring. Seven-jewel watches need a stronger mainspring, and I was able to find an unusually strong one from Cousins UK. A Model 1908 with 17+ jewels will run fine with a .18 strength mainspring, but this guy got a monster .205 strength spring. (It is part number GR7002TR, 2.80 x .205 x 600, should you need one.) Higher force is needed to overcome the greater friction in the gear train. But don’t put it in a 15+ jewel watch—it will knock terribly.
As another small vexation, the watch wouldn’t wind fully: the spring would make a snapping sound after a few winds. When I asked my son what he thought the problem was, he said that the hole in the spring probably wasn’t catching on the barrel’s hook. That kid knows his watches—that was in fact the problem, and adjusting the hook fixed it.
And the Results?
Amazingly, the watch ticked with respectable amplitude in all 6 positions. But after it ran for a few hours, it ticked erratically and then stopped.
The watch succumbed to the fate of all 7-jewel watches: enlarged bushing holes. As we mentioned earlier, the steel pivots enlarge their holes into olive-shapes. This is particularly common for the fastest-moving wheels, such as the escape wheel and 4th wheel. The escape wheel holes were a lost cause.
Adding Some Jewels
So the unhinged quest took a new turn. My son and I broke out the jeweling set and replaced the upper and lower bushings for the escape wheel with friction jewels.
For the upper jewel, I rediscovered my stash of friction jewel converters. You don’t often need these, but they come in handy. Before friction jeweling, watches had jewels that were “rubbed in” to settings and held by a thin lip of metal that was burnished over the jewel.
For a quality restoration project, you should “rub in” a new jewel, which isn’t hard with the right tools. But for a watch with metal bushings, a converter setting will do.
These converters resemble bridge settings, and they have high walls for holding a friction jewel securely. This setting is 2.30 mm wide and accepts a 1.40 mm jewel.
My son ably reamed the jewel hole to a diameter of 2.29 mm, just shy of the 2.30 mm setting. (We don’t have tiny finger cots, so the parts were recleaned after.)
The jewel was pressed into the setting, and the setting into the bridge.
For the lower jewel, we friction-fit a jewel directly into the plate. The plate was thick enough to hold the jewel snug, and the jewel is concealed behind the dial, so a setting would be wasted.
Measuring the Rates
After getting more effort than it deserved, how well did this watch run? I wound it up, let it run for a couple hours, and then, out of curiosity, centered the regulator and measured the rates at full wind.
I must say, I was shocked.
Incredible. The watch is running fast, of course, but all 6 rates are close. The amplitude was excellent (around 300 horizontal, around 260 vertical). And the traces were surprisingly tight and stable. You would expect wavy traces from a 7 jewel watch with a rough steel pin for a roller jewel, but this isn’t too bad (perhaps +/- 4 seconds across a couple minutes).
This watch lacks mean-time screws, so I added a pair of heavy washers to slow it down by 4 minutes. I then let it run for a day to settle down before fine-tuning.
And here are the rates after a day.
Goodness gracious. I can tell that someone had adjusted this watch at some point—it has a few timing washers—and that person must have done a great job. No 7-jewel watch should run this well.
I’m going to leave well enough alone. I’m exasperated with this watch, and it runs better than a 7-jewel watch with a hacked roller jewel and pallet fork should run. I nudged the regulator to set it to around +2 DU, and that’s that—a 110 year old 7 jewel watch (well, 8 jewels, I suppose) that keeps close to railroad time.
If you’re curious, here is what the timing traces look like after the regulator was nudged to slow the watch down a bit. The lines aren’t Illinois or Rolex tight, but they’re pretty good.
The case got a good scrubbing and a light polishing, and then it was time to wrap it all up. And what happens? More bugaboos:
- the dial screws won’t grip the dial
- the watch won’t wind when in its case
- and the mainspring unhooks…again
So it’s back to stripping this thing down and troubleshooting. I don’t know what I was thinking with this afflicted beast. Don’t buy 7-jewel watches—they’re cursed.