I just recently bought a timing machine, which is a huge help in doing adjustments. Basically, a timing machine has a very sensitive microphone that listens to the ticks. The microphone is integrated into a clamp, and mounted onto a nicely articulated base, so that the watch can quickly be placed in any desired position.
The microphone input is compared by the machine to a standard timing source. On my 1970s-era machine, the standard is a quartz crystal(older machines used the 60 hz of AC). The timing of the watch is indicated by a line that's printed on a paper strip. A line straight down the strip means that the timing is correct. A line sloping to the left means the watch is running fast, while one sloping to the right means the watch is running slow. This is an invaluable diagnostic tool, as it can allow you to pinpoint where a problem is in a watch by noting if a sudden rate change occurs at a specific frequency.
Anyway, I was playing with one of my watches on the timing machine yesterday. The few times I'd worn it, I'd noticed that it tended to run fast, but hadn't payed much attention beyond that. On the timing machine, I noticed that the rate was nearly dead on dial up(DU), dial down(DD), and pendant left(PL). In pendant up(PU) and pendant right(PR), though, the rate increased by nearly a minute a day.
Here's the timing strip, with PU being the rightmost section visible.
I looked at the movement carefully, and noticed that, in the PU position, gravity was causing the hairspring to bear hard against one of the regulator curb pins. This effectively shortened the hairspring for the full swing(rather than part of the spring, as is normally the case), and thus cause the watch to run fast.
I made a very, very slight adjustment to the hairspring to alter this. After doing so, I was able to get the watch to rate the same PU as in DU, DD, and PL. Thus, this is now a 4 position watch-pretty good for a watch that was not adjusted to position at the factory. Since PR is a little used position, I'm not overly worried about it. I was, however, worried about PL since it's the "carrying" position-thus I've now made the watch very useable as a carry watch.
It's not often this simple, but this will hopefully give some idea of what's involved in watch adjusting and why it increases the cost so much. It also, though, shows why it's absolutely critical that a RR grade watch be adjusted to position.
