Avoiding The Pitfalls

A poised balance wheel is one that weighs the same at any point on the wheel rim, so any change in the weights will ruin its positional accuracy. This is one of the worst forms of intentional damage because the weights never need to be touched. When a watch slowed from thickening oils, the lazy choice was to grind off the weights to gain time.

Obviously wrong jewels are another sign of damage. Milling a replacement jewel is an exact science with regard to pivot size, diameter, and shoulder thickness, although the new one may not be a perfect color-match. If the balance cap jewel sits too low it probably means that the balance was re-staffed with one that was too short.

Cracked or missing jewels also mean that the watch has been dropped, or worse, that someone separated the plates out of curiosity and then failed to align the pivots, shattering the jewels when screwing the plates back together. Jewels in gold settings are getting very hard to find, so replacements may not be a good color match.

A hairspring is paired to the balance wheel in a process called vibrating, because there's a relationship between the length of the spring and the amount of mass on the balance wheel. Replacing the spring means adding or removing weight to re-poise the wheel and re-time the watch, which is time-consuming and costly.

Incorrect or mismatched screws means that the original hit the floor and couldn't be found. Most American factories chose unique thread pitches to ensure that only their material was used, so an obviously wrong screw likely means that it came from a different brand with different threads, which are now stripped.

Broken or missing parts may be difficult to replace, especially if the watch is a rare variant or the factory had a short run. It's common to find certain parts broken, such as lever springs, since not all designs were good ones and the part failed because of this. Others were simply discarded, like stopworks and regulator springs.

Wartime material shortages meant using acrylic (plastic) for crystals, which yellowed and trapped moisture, causing the hands to rust. If your piece has a glass crystal and the hands are still rusted, then the watch was probably stored for years in a damp location, which means that most of the internal steel components will have nascent corrosion.

Case screws with partial heads made it easier to mount the movement because they could be pre-loaded, but full-headed screws had to be threaded in later. The problem with half-headed screws is that the leading edge acts as a drill flute, eventually grinding their way completely through the case rim, leaving no metal, so the only option is an ugly washer.

 Ghost marks are ugly scrapes caused by case screws from other movements, meaning that the one in the case is not the original. While this is not critical, original combinations are generally worth more. After repeated swaps a movement may end up in a replacement case that's a poor fit, or has incorrect stem depth, misaligned lever cutout and more.

When a watch falls, one or both balance pivots will likely break. The first one that breaks will allow the balance wheel to twist, and the leverage placed onto the pivot at the opposite end is enough to shatter the brittle hole jewel.

Why does the balance staff always suffer? It's simple - the ratio of mass to the pivot size of the balance wheel is the highest of any component within the gear train, so if the watch falls then one or both balance pivots will very likely bend or break off.

If the balance staff is original, the rivet that holds it to the wheel will be finished flush like in the above photo. All of the staff's dimensions will be correct with regard to overall length, balance seat, hub height, hairspring and roller seat, and pivot size.

When a staff breaks, a tinkerer will usually  buy a single staff off eBay, but that person won't bother to measure it for any of its seven dimensions, convinced that all balance staffs are the same size and that the eBay seller sold them the right thing.

If the replacement staff is wrong then the balance wheel could sit too high, rubbing against the underside of the balance cock or the regulator arm. In this photograph the tinkerer filed down the regulator arm in an attempt to make room for the wheel.

If the replacement staff is wrong then the balance wheel could sit too low, slowly grinding a mark into the upper plate and permanently scarring it. In this photo the tinkerer never bothered to check if the wheel was clearing the plate.

If he locates the right balance staff and doesn't own a decent staking set, our tinkerer will try to install it by gluing everything together - the staff, the wheel, the roller table, and roller jewel. Cyanoacrylate (Superglue) makes a brittle bond and will eventually fail.

If our tinkerer has a quality staking set he will try to rivet the new staff to the balance wheel. Assuming that the fit is correct, the rivet still must be dressed by milling it flat and flush with the balance arms. In this photograph that clearly was not done.

If the balance seat diameter is too small, the tinkerer will simply hammer away at it until the metal spreads enough to trap the wheel. This will cause the rivet to crack and weaken, and the staff won't center itself in the arbor hole, so the wheel will wobble.

Some tinkerers will heat the broken staff to soften the metal before punching it out. Of course, all this does is overheat the balance wheel and hairspring, removing the temper from anything made of steel. The hairspring in this photo is ruined.

If our tinkerer ruins the existing wheel by making the arbor hole oval and ragged, he could use a wheel from a different watch and just scratch out the serial number. The donor wheel won't have the same mass as the old one, and the accuracy will suffer.

If the hairspring seat on the replacement staff is too large then the collet will break when our tinkerer gleefully pounds it back on. This is by far the single dumbest, most expensive mistake of all because replacing a collet is both time-consuming and costly.

The same goes for the upper roller table and the lower table and the spacer if the staff is double-roller. If the dimensions of the replacement staff are too large, then the table will break as the tinkerer is happily pounding it on with his mighty hammer.

If our tinkerer breaks the roller table he might use Superglue or epoxy to try to glue it back on. Again, this is a very poor bond and will eventually fail, allowing the parts to fall off into the gear train, which is just what happened in this photograph.

If our tinkerer is really dazed he'll fail to fully seat the roller table and not bother to check under the stereoscope. If the roller table is sitting too low it will hit the pallet arm and if the roller jewel is sitting too low it will strike the plate, stalling the watch.