Pallet Jewel Lubrication and Amplitude

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Amplitude is the big thing in watch adjusting. If the balance wheel doesn’t swing at least 270 degrees dial up and down and at least 220 degrees in the vertical positions, it isn’t ready to be adjusted to positions.

Proper lubrication is necessary for good amplitude. “Which oil is best?” is one of those evergreen “forum fight” topics. Everyone has a favorite, and there’s a dizzying array of oil choices. Notably, watch companies like ETA and Rolex hint that watchmakers who dare to deviate from the recommended oil brands might awake to find that fiery asteroids have rained down from the heavens upon their workbench.

Pallet Oiling and Amplitude

It’s easy to get cynical about oils, which are freakishly expensive. But specialized oil for the pallet jewels is worth the money.

In the classic lever escapement, the teeth of the escape wheel slide across the impulse faces of the pallet jewels. If the teeth and jewels are dry, the friction reduces the impulse ultimately given to the balance wheel. And this reduces amplitude.

For an example, here’s a Hamilton 4992B, a WWII military watch that I’m cleaning for a friend. This watch got a new mainspring and was cleaned and oiled—but the pallet jewels were left dry. Here are the dial-up timing readings.

Two things stand out:

  • The amplitude is only around 255, which is much lower than you’d want for a newly cleaned and oiled watch.
  • The traces are ragged and uneven instead of clean and parallel.

Time for some oiling. Pallet jewel lubrication is particularly tricky because of the impact involved. The escape wheel’s teeth hit the locking face and then slide across the impulse face. The force and motion will cause a light oil, of the sort you’d use for balance jewels, to splatter. Over time, amplitude will suffer as the pallet oil disperses and degrades.

Moebius 9415 is a popular oil for pallet jewels. It’s a gloppy grease that liquefies on impact. Unlike a light oil, 9415 stays in place and won’t splatter, so amplitude will be reasonably stable over the long run.

I placed some 9415 on the pallet jewels. Only a little is needed, and it’s easy to overdo it. I let the watch run for a day so the oil could distribute evenly on the escape wheel teeth.

And here’s the result.

The timing traces are clean and parallel, and the amplitude is almost 50 degrees higher.

Another solution, by the way, is to design away the need for oiling. For example, George Daniels designed his famous coaxial escapement to run without oiled pallet jewels. But unless you’re working on your Omega Coaxial 2500, care in pallet oiling will pay off in amplitude.