I installed a new mainspring in a Rolex calibre 3000 recently. Cleaning, adjustment, and assembly of the movement all went smoothly and when I put the movement on my timing machine for initial timing, it timed out great. My amplitude however was almost off the charts. Very unusual.
I double checked the engagement of my pallet stones with the escape wheel. They were perfect when I checked them the first time and just as much so when I checked them the second time around. If the engagement of the pallets had been a bit on the shallow side, I could have attributed the unusual amplitude to that, but they were fine. So that wasn’t it.
I listened carefully to the mainspring glide smoothly along the barrel wall at full wind, exactly as it should. If there wasn’t enough thixotropic grease, the mainspring could snag on the barrel wall and cause an excessive amount of power to be transmitted through the gear train, which would result in higher amplitude. Alas, that wasn’t the problem either.
I double checked the endshakes on the wheels through the gear train and at the balance wheel. Nothing was awry. Had they been excessive, it could potentially have been the issue, but not to the degree I was seeing. Endshakes can be a big contributor to a lack of amplitude if they are too tight, but rarely might they cause excessive amplitude. I would have been very surprised if excessive endshake proved to be the cause, but figured that double checking them was at least worth a shot. No luck.
On the surface, everything was checking out flawlessly. The only problem that lay before me was the very possible danger of the roller knocking if I couldn’t tame the amplitude.
Just shy of deciding to pull the pallet stones way out, I decided to double check the package of the fresh mainspring I had installed. Turns out, I had somehow mistakenly ordered and received a mainspring for the calibre 3035, which is a substantially more powerful mainspring than the one used in its littler brother, the 3000. A simple change to the correct mainspring and everything was back on track and running perfectly. Amplitude included.
Save yourself a potential headache and double check part numbers! I try my best to always do so, but interruptions to serve clients, phone calls, and other distractions in the shop can sometimes get the better of me. On the bright side, it’s another lesson learned and if it ever happens again I’ll be able to save valuable time by checking the package sooner. Hopefully, knowledge of my blunder will save you some time down the road one day, too.