To put a balance wheel in poise, we add weight to the lightest spot or remove weight from the heaviest spot. What are good tools for adding weight?
Balance Screw Holders and Removers
First of all, you’ll need a way to take the timing screws off and on. Balance screw holders—also called balance screw removers—are essential. Trying to do this with screwdrivers and tweezers is the route to madness.
Balance screw holders are essentially pin-vises with tip diameters that vary in size. The ends are tapered to allow them to slip over a screw without bumping into the one next to it.
You’ll need several sizes. If it is holder is too large, then it won’t grip the screw. And if the holder is too small, it will gouge and mar it. As a result, don’t buy a balance screw holder unless you know what size it is. Ideally, you’ll find a set of holders.
It’s best to first loosen the screw with a screwdriver and then grab it with the holder. When replacing the screw, you can thread it in most of the way with the holder and finish with a screwdriver. This reduces the chance of stripping a screw.
Some tools combine a screwdriver blade with a balance holder. Here’s a fun vintage K&D tool that you might find useful. It has spring-loaded jaws that surround a thin screwdriver blade. You slightly unscrew the screw with the blade, push the end to open the jaws, and then grip the screw. You’ll find these in 2 sizes, for wrist and pocket watches.
Like many tools, this combination holder has fans and detractors, but I find I use it most of the time.
You add weight to screws by slipping timing washers between the screw and the balance wheel. Timing washers come in assortments of different diameters and thicknesses. Each washer has a timing rating that reflects how much it will slow down your watch. These rates are given for different watch sizes. This guidance is very general, at best, but you’ll develop an intuition for it eventually.
Timing washers for wristwatches are inexpensive and easy to find. These are much thinner and smaller, naturally, so they won’t work for pocket watches. Even the largest washers in the assortment in the picture, for example, won’t fit over the threads of a Hamilton 6/0 sized watch.
Timing washers for pocket watches are harder to find and much more expensive, but the basic ideas are the same.
In his book, de Carle suggests putting the washer on the mat, licking your finger, and dabbing it on the washer. Using your screw holder, you can then spear the screw end through the washer and thread it back into the balance. This is unseemly but effective.
In his book, Kleinlein pointed out that some of his contemporaries disapproved of using timing washers to add weight. It’s true that timing washers can stand out visually, especially on larger pocket watches, when they have a bigger diameter than the screw.
An alternative is to fit a new, slightly heavier screw. Realistically, you’ll rarely add weight by swapping screws, but it is an option if you have the parts and inclination.
In old-time repair shops, an adjuster would have assortments of balance screws for different manufacturers and grades. Such assortments are hard to come by these days, but you can salvage screws from a scrap balance. I often do this when working on a watch with screws that have been gouged by balance cutters.
You occasionally see balance screw scales—teeny-tiny scales used to judge the relative weights of screws—for sale, and you’ll need one to ensure that the new screw is slightly heavier.