The Joy of Precision

Not too long ago, I discovered that a friend of mine had this nice little 15 jewel Illinois pocket watch.  It had apparently been passed down to him, but he had never seen it running.  At a cursory glance it appeared to have a broken mainspring (or a mainspring that had slipped off the winding arbor), but a good balance.

Once I uncased the movement, it became clear that it had been dunked completely in oil.  It is hard to say whether someone genuinely thought this was how to oil a movement, or if it was a sledgehammer approach to prevent rust… whatever the reason, it turned into a real chore to clean up the mess.  Here you can see all of the oil pooled up underneath the dial.  Most of it could not simply be mopped up, as it had thickened into a hard, gummy paste over the years.

You can’t really tell in this picture, but the oil is caked up around the regulator as well as the pallet fork and hair spring.

Of course, the pools of oil didn’t stop there.  Here you can see it pooled up around basically every component in the gear train and underneath the mainspring barrel (it was also pooled up inside the mainspring barrel):

It turned out to have a broken mainspring, so I ordered a new one and proceeded to inspect the rest of the movement.  I ended up finding a cracked fourth wheel jewel.  Here are a couple of pictures that I took of the cracked jewel, through a stereoscopic microscope:

I rummaged through my assortment of spare jewels and found one that was the correct size, although the brass housing was too thick to give the proper end shake.  The setting was chucked into the jeweler’s lathe using a “jewel chuck” (a small, specialized collet) and turned to the appropriate thickness.  Here is a picture of the new jewel, installed in the bridge, next to the jewel chuck that I used:

And here a couple of extreme closeups of the new jewel in place:

With the mainspring and fourth wheel jewel replaced, and everything cleaned and properly oiled, the movement ticked to life once again.  Here it is running, before I installed the micrometric regulator:

Here is a shot of the broken mainspring and the dial, which had just been cleaned using denture cleaner.  In the background, you can see the movement, covered, and ticking away merrily.

And here is the completed watch: