Among amateur watch repairers, it is good advice refuse to work on antiques or valuable heirlooms. Doing so without sufficient experience can lead to frustration! Old watches also have non-standard parts and other oddities that can trip up the unsuspecting would-be repairer. I have followed this advice until recently... and ended up in a bit of an adventure.
What tempted me down this path was an antique heirloom watch that was in very poor shape.
It was apparently my great grandmother's watch. It is quite pretty, but when I received it, it had not been well kept by its owner. Furthermore, it had been to some very poor watchmakers! Slowly, over the course of three years, I made a number of repairs, none too difficult:
- I replaced the missing glass with an acrylic face.
- The case wouldn't close because it was slightly out of round... I put it back into the round, so the case opens and closes correctly.
- I remade a case screw that someone had snapped the head in half (!). There are marks on the plate where the screwdriver skidded off after snapping the screw, so clearly way too much force was involved. Ouch!
- The winding stem that was acting up, because a brake was tensioned incorrectly.
- I put the hairspring back in order because it was twisted badly.
- Finally, recently, I took the movement apart and cleaned it. This was completely uneventful.
It now runs reliably, but gains about 5 minutes per day. That's terrible, of course. But given that I don't have a replacement hairspring and given the age of the watch, it's well within what I'm willing to tolerate.
I had a very different experience -- and it's not over -- with a watch from my wife's family.
This watch wouldn't run, but didn't have anything visibly wrong with it. Upon disassembly, I found that the lever fork cock was ever so slightly bent and was pinning the fork down. Since it couldn't move very well, that kept the train stuck. That wasn't the only problem...
As I was reassembling the balance, I was a bit less careful than I should have been. I noticed the balance was not able to turn freely in both directions. The balance was simply on the wrong side of the fork, and needed to be carefully lifted over the fork. Unfortunately, I couldn't visualize what was wrong. Instead of the correct move, I gave the balance a sound push the other way. That was not a good plan, and I really did know better! Disaster! The impulse pallet jewel was shattered!
After carefully sizing the missing pallet (seems to be about 19/1000"), I realized that it would be useful to make the pallet out of blued steel. It should have nearly the same characteristics, and it should "just work." (I also ordered a ruby impulse pallet, but I'm not confident of my measurements...)
It took five tries to make and install the impulse pallet, because I lost the first three pallets I made, and although the fourth worked, it was very poorly made. The fifth looks nice enough and seems to be working.
Of course, the first step was to disassemble the balance. I removed the old pallet by heating the roller table with a soldering iron with a fine tip at roughly 250 degrees F. Using a needle, I cracked off all the old shellac.
First, I trued up the end of a 0.5mm blued steel rod, using an arkansas slip.
After truing, I rounded and burnished the end. Next, under the microscope, and on a soft piece of wood, I ground a flat surface using the arkansas slip. In the picture below, the flat is visible as the slight smear at the end of the rod. (The flat is about 1 mm long.)
This made the rod into a D shape. I kept grinding the flat until the rod barely entered the hole in the roller table. Then, I burnished the flat surface.
Unfortunately, the rod was too large to fit the slot in the lever fork.
So, I ground a fine taper to the rod by hand, by eye, under the microscope until the rod would just barely bind in the lever fork as I rotated it with the tip in the fork.
Then I switched to a steel burnisher to smooth the surface of the rod. After burnishing, the rod freely fit the lever fork, with the base of the taper still fitting the roller table.
To cut the pallet off the rod, it's important to cut it to the precise length. Since I ended up making five pallets, I was able to zero in on the correct length by comparing with an earlier attempt. But in any case, I reversed the rod in the pin vise, and then used a narrow file as a saw to slice off the pallet.
Once again, I switched back to the arkansas slip to true the end, and then polished it with the burnisher. Even though this cut end is completely invisible, this was an important step because the cutting raised burrs. Burnishing removed those burrs.
OK, now the pallet was small! It's the apparent "grain of sand" on the left of the frame in the balance cock in the picture below.
Getting the impulse pallet into the hole in the roller table was... irritating. The pallet is slippery by design, and rounded... which means that holding it too tightly (or gripping the wrong surface) with tweezers will launch it across the room. I lost three attempts irretrievably and lost another one for a very long time. Eventually I got it pressed in place.
To anchor the pallet, I gripped the balance in surgical clamps and applied shellac.
Someone before me was way too liberal with the shellac and glued together several turns of the hairspring. I was able to knock them apart, but if it impacts timing, I may have to immerse the spring in alcohol. I'm loathe to do that because the spring has a nice overcoil and is very, very delicate!
Here is the balance reassembled with the new impulse pin installed in the roller table.
And a zoom-in:
But the balance reassembly did not entirely go well the last time... I bumped the attachment point with the tweezers, and snapped the spring at the balance attachment point. Previously, I had thought it nice that there was a removable clamp that made removing the balance easy. However, that clamp was installed very permanently onto the hairspring. It took a good two hours to remove the old pin (brass, extremely tightly fit; I think it was staked in place at the factory!), fashion a new pin (I used soft copper, and much longer, since I wanted be able to get it out in the future if needed), and get everything back to working order. As wooden clockmaker Clayton Boyer says,
"Mistakes take a lot of time. I spend some of my best woodworking time making them." Yeah, I agree.
Still, after all that, the watch still would not run. What!?! No visible trouble... actually, not. I had never worked with a watch with an overcoiled hairspring. It can happen that the overcoil turn can foul on both the balance cock
and the main turns of the spring. That was the problem. A very slight touch on the spring attachment point fixed the overcoil's path, and the watch sprung to life!
The movement is now running, which is a relief! It sounds different from the other movements I've repaired, because it's quite a bit lower frequency (around 2 Hz) than other movements of the same size (typically 4-6 Hz). Assuming it all goes back together, I wonder if it will keep reasonable time?
One final thing, though. The winding works for this watch is not the usual Swiss mechanism. It's a bit simplified, which seems elegant at first. Here it is when correctly assembled.
However, should the stem get loose and you simply try to reinsert it, you will likely knock the cylinder gear assembly off its retaining spring. This is rather subtle. In the picture below, the lower retaining spring is supposed to be running in the cylindrical groove right below it. All you need to do to repair it is slip the stem back in, and push the spring down gently. It reseats easily, and then you can carefully withdraw the stem, leaving everything in place.
This process is extremely annoying, because although fixing it takes mere seconds, to access this mechanism you have to uncase the movement, dismantle the hands, and dismantle the dial. Reassembling the movement into the case involves reinserting the stem, which has a tendency of knocking the winding mechanism out of order... so you need to back up, disassemble everything and try again...
