Pocketwatch 101℠ – Learn about Vintage and Antique Pocket Watches
The "Problem" with Seven-Jewel Watches
Why more jewels in a watch are usually better than fewer jewels!
If you're new to vintage watch collecting, you may not know what types of watches to look for and which would be best to avoid. You're also probably not an expert in assessing the internal condition of a vintage watch... at least not yet. Or, perhaps you're looking to have your vintage watch repaired and want to know if it's "worth it" to fix your watch. While that's a question that only a watch's owner can ultimately answer, as a general rule we don't encourage the purchase or extensive repair of low jewel-count watches unless they hold special sentimental value for their owner. In many cases, the cost of reparing a seven-jewel watch can exceed its worth.
Now before we get a bunch of angry email from proud seven-jewel watch owners, let me say that there are some fine examples of seven-jewel watches out there that have been used little and are in excellent condition. And there are many beat-up, non-working seven-jewel watches that are still prized family heirlooms just because it was great-grandpa's watch. But... there are built-in limitations in a seven jewel watch that make them more susceptible to wear, and sometimes impractical (or more expensive) to repair.
The jeweled-lever escapement
Most vintage mechanical watches made in the last 150 years are designed with a "jeweled lever escapement." Jeweled levers make up the vast majority of commonly encountered vintage watches found today. Jewels are used in a watch as bearing surfaces at key points of friction. A polished jewel is good for this purpose because it is very hard and can be made very smooth, thus reducing friction and wear. [ Learn more about jewels in watches ].
In a jeweled lever watch, the first seven jewels employed in the construction of the watch are (typically): 2 balance hole jewels, 2 balance cap jewels, 2 pallet jewels, and one impulse (or roller) jewel; that is the jewel arrangement you'll find on virtually every seven-jewel pocket watch. The pallet and roller jewels are key parts of the escapement. They control the release of energy from the watch's mainspring, through the gear-train, to the balance, allowing the energy to "escape" in a controlled fashion... thus the name "escapement".
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Jeweled and non-jeweled bearings
A jeweled bearing, which supports the "axle" (staff) of the balance or train-wheel, allows the wheel or balance to run with minimal friction as the polished wheel-pivots only make contact with the hard surface of the polished jewel. In a seven-jewel watch, the only moving wheel that runs in jeweled bearings is the balance wheel. All of the other gears in a seven-jewel watch are not supported in jeweled bearings; the steel pivots turn in a hole in the brass plate instead of a jewel, and are thus subject to greater friction and wear. Since the hardened-steel wheel-pivots are much harder than the surrounding brass, the wear is concentrated on the brass plate.
Asymmetrical jewelling on Elgin Mod 5 shows difference between jeweled and non-jeweled wheel-bearings.
Wheel-pivots on the visible side (left) run in jewels on 3rd, 4th and escape wheels;
wheels-pivots on non-visible side (right) run in holes in the brass plate.
Why 7-jewel watches can be a problem to repair
The gears on an old pocketwatch operate under a lot of spring tension, especially on 12, 16 and 18-size pocket watches with strong blue-steel mainsprings. As the watch is running, the gears turn round and round, and the steel axle of the gear under all that spring tension gradually wears away at the side of the hole that it rests in. This is even worse if the watch is run without adequate lubrication, or if abrasive dust or grit gets into the movement.
The photo above shows the 4th wheel pivot
projecting through a badly worn hole in ther
uppe plate of a 7-jewel Elgin watch. The pivot
has carved a new offset hole that's nearly as
big as the original hole!
Some lower-grade Elgin watches seem to be particularly susceptible to this problem. The oil-sinks (the little "well" in the plate that keeps the oil around the pivot) on those watches are a little too deep, which makes the bearing surface of the hole quite thin. As a result, these plates can wear out quickly if run dirty or without adequate lubrication as shown in the photo.
The wheel pivot will eventually enlarge the hole in the brass plate just like a tiny file, and since it's being pushed by spring tension, it will tend to elongate the hole in one direction until the hole is no longer circular... it becomes egg-shaped. When the hole becomes oval or egg-shaped, the axle of the wheel begins to wander off vertical, and the wheel depth (how one gear meshes with the next) is affected. When this occurs, friction can increase and power-transfer from the mainspring to the escapement becomes much less efficient. The gear-train is no longer able to do its job. In severe cases, the gear train will bind and the watch will no longer run.
The problem of enlarged plate holes does not occur in watches with higher jewel-counts, because these watches use jeweled bearings on most or all of the gears. The jeweled bearing presents a hard surface which does not wear like the steel-on-brass grinding which occurs in a non-jeweled bearing.
Enlarged plate holes
This same problem can occur in old
clocks with brass plates. The photo
above shows an enlarged hole in a
brass clock plate. The hole should
be circular... not oval.
Unfortunately, the "seven-jewel problem" isn't a simple problem to correct. Over the years, watchmakers have made numerous attempts to deal with enlarged, ovoid plate holes. Sometimes we see watches where the holes have been "punched"... where someone had attempted to "close" the enlarged holes by raising little divots in the brass plate all around the hole in an effort to force material back into the hole. Needless to say this is a crude solution that doesn't hold up well.
The only "real" way to fix the problem would be to correct each of the enlarged holes in the plate. This could be accomplished by drilling out the hole to a larger size and fitting a small brass bushing (buchon) which would then be sized to exactly match the thickness of the plate. This would, in essence, mend the enlarged hole in the plate with new brass. Then a new hole can be made, making sure it's exactly the right size and in exactly the right position so that the wheel depth is correct. It's a job which requires precise skill and the right tools... and it's quite time-consuming. In most cases the value of a seven jewel watch does not warrant this sort of repair investment.
Another potential solution would be to cut out the enlarged holes in the plate and install jeweled bearings at each of these locations instead of brass bushings, which would then likely force changes in the wheel pivots. This could be made to work... essentially "upgrading" the watch to a higher jewel-count, but again it's just not a very practical approach for most 7-jewel watches.
The bottom line on seven-jewel watches is that they simply wear out over time. Unlike a fully jeweled watch which can, with care, be kept in excellent condition for generations, a seven-jewel watch has a finite lifetime, as determined by how long it takes to wear out the non-jeweled plate holes. At that point, it becomes no longer practical to repair.
Better to stick with fully-jeweled watches
To sum up: the time and expense required to properly restore the excessive wear that we often find in seven-jewel watches would, in many cases, exceed the practical "value" of the watch. In those cases, it only makes sense to invest in a repair if there is extraordinary sentimental value attached to the watch that would warrant the expense.
For this same reason, a seven-jewel watch is also probably not the best choice if you are looking for a vintage pocket watch to fix up and carry on a daily basis. Because of the inherent limitations of the seven-jewel design, the watch will simply wear-out with enough use, and keeping a seven-jewel watch in working condition will require more frequent maintenance than would a more highly-jeweled watch.
So if you're a collector or a watch buyer, your money is probably better spent on "fully-jeweled" watches of 15-jewels or more. Those seven-jewel "fixer-uppers" can often be prohibitively expensive to repair because of their built-in limitations.