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FROM THE BENCH: Watch Regulation — Other Methods and Vintage Designs

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FROM THE BENCH: Watch Regulation — Other Methods and Vintage Designs

This is part two of a three part series about watch regulation. Read Part 1 here

Oak & Oscar watches use the most common form of regulation, but there are other options.

In the previous article, we discussed regulator arms' mechanics and pros & cons. Now let’s look at some other ways that watches have been adjusted throughout the years.
Free-sprung balance in a fine Swiss watch movement
Regulator arms’ biggest disadvantage is that the hairspring is constantly being touched and affected by the regulator pins; balances can most easily keep a stable rate when left alone. So, some watches use what’s called a “free-sprung balance.”

As the name implies, free-sprung balances let their hairsprings dance without interruption from any regulating device. So how does it keep time?

Besides the length of the hairspring, there’s another component to regulation: the effective mass of the balance. Typically, this is a fixed number, but free-sprung watches can’t vary their hairspring, so the balance wheel is adjusted instead.

Removing weight from a balance wheel through drilling is possible, but destructive. Adding weight, though possible, is fiddly. Instead, free-sprung balance wheels use adjustable weights that can be moved toward and away from the wheel’s axis, varying the wheel’s moment of inertia. While the actual mass of the wheel is unchanged, its effective mass moves in and out, causing the wheel to spin faster or slower—like a figure skater spinning faster as she moves her arms inward.
Adjustable timing weight in a fine Swiss watch
These little weights can be made in a variety of ways. Some manufacturers cut tiny gold screws threaded into the rim; others use C-shaped gold eccentric weights which fit on posts and can be rotated in and out. Whatever the method used, the concept is the same—weights toward the center make the watch run faster, and weights toward the outside make it run slower.

So why doesn’t everyone do this? Regulating weights are tricky, expensive, and hard to adjust properly. Worse, they’re easy to adjust improperly, and an unskilled watchmaker can make a real mess of timing in a hurry if all the weights aren’t moved evenly and identically. You also lose the ability to have a fine adjustment screw and equalize positional errors with the regulator.

Regulating screws made a lot more sense in the past when the balance rim was absolutely riddled with them. Looking at this balance from a vintage pocket watch, you’d think that it is being regulated like crazy, but in fact, only two of those screws are for regulation. The rest are all for temperature compensation, which we solve in different, more elegant ways.
Balance wheel in a vintage Howard pocket watch movement
Vintage designs didn’t always pick one or the other, though. Many pocket watches will come with timing screws and a regulating arm, the idea being that you get the timing pretty close with the screws, and finish the adjustment with the fine regulator. And oh, how beautiful some of those regulators can be!

Fine adjusters can have some of the most elaborate engineering and decoration in any part of the movement. “Swan neck regulators” are still commonly used in high-end watchmaking simply because they are a classic design, and extremely difficult to finish at a high standard.
Swan-neck regulator in a vintage pocket watch movement
They function similarly to the eccentric screw design on Oak & Oscar watches but rely on tension from a bent spring (the eponymous swan neck) to provide tension against the mechanism to keep it stable.

Similar designs rely on geared or otherwise screw-powered designs (proper screws, not eccentric “screws,” that is) which are highly precise and stable. Since they don’t rely on friction, they’re less susceptible to being affected by bumps—though not immune from shocks, since impacts can also alter a hairspring’s shape, which has a major impact on timing.
Fine regulator in a vintage Elgin pocket watch movement
To maximize accuracy, many of these screwed regulators have extremely long “pointers,” allowing the watchmaker to carefully and repeatedly achieve proper adjustment. These elaborate pointers can be works of art in and of themselves. Just look at this incredible curved threaded rod, along which a tiny sleeve nut pulls the pointer. Cutting threads at this size is incredibly difficult, and curving them … that’s something else entirely.

The pointers are traditionally made from steel, polished to perfection. Hardened steel can take on a brilliant jewel-like shine when properly polished—traditionally by hand, with diamond powder—and black polished steel regulators are one of the great traditional highlights of haute horlogerie.
If this sounds familiar, I briefly touched on polishing in the article about gentian and whiskey Old Fashioned Cocktails. Yes, it’s all related!