In the days before smooth balance wheels, the mass of the balance wheel was controlled using screws around the rim of the balance wheel. This approach enables relatively fine control over a wheel’s poise by adding or removing weight to specific spots on the wheel. It isn’t as aesthetically elegant as a smooth, one-piece wheel, but it was a good solution for the state of watch manufacturing of the day.

There are many ways to remove weight from a balance wheel, but only a couple ways to add weight. One way is with timing screws, which are simply replacement screws that are slightly heavier than the current ones. Timing screws are a sledgehammer approach to adding weight. They are mostly used when the existing screws have been hacked and botched. For finer control over weight, however, timing washers are indispensable.

The Basics of Timing Washers

Timing washers are tiny washers that come in a variety of materials and sizes. Larger washers, naturally, will have a greater slowing effect on the rates.

The boxes they come in will give some guidance about the washers’ effects based on the size of the watch. Needless to say, these are rough approximations at most. Your mileage will surely vary depending on the watch at hand.

If you see a good assortment at a good price, snatch it. Wrist watch washers are easy to find; washers for large pocket watches are the most sought after.

A timing washer will slow down a watch via two effects. First, and most obviously, it adds weight to the balance wheel. Second, it displaces the screw outward from the balance wheel. By acting as a “spacer” of sorts, it affects the wheel much like unscrewing a mean-time screw would.

There are two basic applications of timing washers.

• Regulating the watch’s overall rate. To greatly slow a fast watch, you add a pair of identical washers to opposite ends of the wheel. This method is handy when a watch lacks mean-time screws and when you want to avoid pushing the regulator arm all the way over to the “slow” side.
• Adjusting via improving the wheel’s poise. And, of course, you can place a single washer on the balance wheel’s light spot. This will slow the watch and improve the wheel’s poise, thus reducing timing differences in the vertical positions.

We’ve seen examples of these two basic applications in many, many of our “example watches” posts.

Some Quirky Tips and Tricks

When you’re aiming for really fine control of a watch’s rate, you will sometimes need some unorthodox approaches to timing washers. Here are a few tips and tricks.

Ream the Holes of Tiny Washers

Sometimes a timing washer is too heavy—it has a greater effect on the timing than you want, but the smaller washers won’t fit. It’s common, in fact, for the inner diameter of a timing washer to be too small to fit over the thread end of your screw.

In this case, not all is lost. You can ream the hole of the timing washer to enlarge it. This allows you to use very small, light washers on relatively larger screws, so you can make tinier, more precise changes to the timing.

A simple method is to place the method in a bench block or a spring-loaded vise used for reaming watch hands.

Make Thinner Washers Via Filing

When a washer is just a little bit too heavy, I like to reduce the weight by filing it. This reduces its thickness and weight and gives fine control over the washer’s effect on the timing.

A simple method uses jeweler’s polishing paper, a flexible paper with embedded abrasives. Simply rub the washer on the paper in a circular motion, polishing it and stripping away a fine layer. Be sure to clean the washer before reinstalling it to avoid lint or dust.

This sounds like overkill, perhaps, but filing a timing washer allows for precise changes to poise when you’re working on a watch and don’t want to remove weight from the wheel.