How did that happen?

Every now and then I get a watch in for repair and wonder how on earth it came to be in this particular state. In this case I received a year old Marathon automatic watch on my bench. Apparently it wasn't winding properly. "Hmm, ok, let's see.... oh, yes, I see what you mean. That doesn't feel good at all... right let's open her up and have a look inside." My train of thought went something like that.
So here's what i found once I pulled the automatic winding out to have a look at the manual wind component.

Can't see it?
Well it is pretty small. Have a really close look at the gold coloured wheel with the big screw head in the middle of it, just where it meets the steel wheel with the even bigger screw head. Still having trouble? Ok, let's use the microscope.

Ah, here we go. Four teeth completely gone, and the rest damaged.... So.....

HOW DID THAT HAPPEN?

Honestly, I have no idea. Customers ask me this sort of thing all the time. I point out damage to their watch, and they ask me how it happened. I don't know. But I do know how to fix it.

In this case, there was only one solution, and that was a full strip and clean of the watch, along with a replacement wheel.

WHY NOT JUST REPLACE THE BROKEN WHEEL?

Well you see, when a part comes off a wheel or lever or whatever, it tends to rattle around inside the watch until it can find the most amount of damage to do. I was kind of curious to see if I could find the missing teeth. I found two for sure. Here they are.

One stuck to the escape wheel.

And one (or maybe more) ground to dust under one of the reversing wheels in the auto winding system.

Once the strip and clean was done, it was all fairly simple. Put it on the regulator to check timing (which was bang on), case it up and water pressure test it.... Oh no wait, it wasn't quite, was it?

It is fairly common practice now for service centers to charge you for a new set of hands when they service your watch. Why?
Because they frequently get damaged during removal. In this case, the hour hand did not want to come off. It was so tight on it's wheel, that the hand started to peel off it's collet, bending itself in the process. In an ideal world, this collet would end above the level of the dial, so that any hand removal tool could grip under the collet, and pull it off cleanly. But this isn't an ideal world, and I could not get the tool under the collet. Rather, it pulled against the soft part of the hand and bent it. These hands hold vials of tritium gas which means they glow for 20 odd years without the need to collect any light first, so I had to be super careful not to damage them. Finding new ones could be very difficult. In the end I gave up trying to remove the hour hand, and just left it and it's wheel on the dial. Not ideal, but the best thing to do in the circumstances. I then had to line it up with the midnight date change when re-fitting it, and then straighten it, as the tip had ended up pointing up in the air. All this without doing any cosmetic damage to either hand or dial.

Well, it worked. This photo was taken after refitting.

Done.

All that remained was to test it and return it to it's happy owner, who asked me "It won't happen again will it?" To which I could only honestly reply "Dunno... I still don't know how it happened in the first place."