Recently I was asked to service a fairly old Rolex automatic wrist watch. This was a caliber 1066, which to be honest I hadn't seen before. There was one problem: One of the wheels in the automatic winding system had damaged or missing teeth.
Checking around my various suppliers, I couldn't find a suitable replacement, so I spoke to the customer about cutting a new wheel. I have cut quite a few wheels for clocks in the past, including making up a whole wheel, pinion, and arbor to replace one that was missing completely from a grandfather clock, but cutting something small enough for a watch was a new on on me and could prove to be quite interesting, so I agreed to do it for a fairly modest price.
The first part of the process is to count the teeth and measure the wheel to ascertain what size cutter to use. My calculations told me a .14 module cutter should be the closest fit, and a week later I had my new cutter from PP Thornton in England. It was considerably smaller than any other cutters in my collection, so the first machining job was actually to make a cutter arbor. Obviously this had to be absolutely exact, so after machining most of it in the lathe, I moved it to the milling machine to cut the seating for the cutter itself. I was very happy with the result of this. The cutter ran true with excellent repeatable accuracy.
It would have been easiest to simply make a new wheel from scratch and just not cut any spokes. I'm sure this would have been perfectly adequate too, but a bit of professional pride made me want to preserve as much of the original wheel as possible. So the next machining job was to remove the broken teeth from the wheel. To do this I faced, drilled and reamed a piece of brass stock so the pinion was a tight press fit into this mandrel. I then fitted another brass blank machined to fit around the arbor, and clamped the wheel in place with a live center in the tail-stock ram. It was a fairly simple procedure to then remove as much wheel rim as required.
Cutting the actual teeth is always the interesting part in a job like this. I turned and bored a piece of brass stock in the lathe, before transferring the chuck to my computer controlled rotary table on the milling machine. This is a truly great bit of kit. I can cut any number of teeth I want with perfect accuracy. In this case it was 52 teeth, so that number was plugged into the key pad, and away we went. I'll spare you the details of exactly aligning the Y and Z axes of the mill to place the cutter in the right place. What I will say is that it took a couple of test pieces checked under the microscope before I got it perfect.
At this point, the wheel was removed from it's arbor and dropped into the recess I had bored in the wheel blank. The stock was held in the big bench vise and heat applied with a small gas torch. A wee bit of flux and solder later the wheel was soldered cleanly in place. Sorry I didn't get photos of this. The wheel was then re-mounted in the lathe and carefully parted off the stock. I stoned off the excess with a Degussit stone, cleaned it, remounted the wheel on it's arbor and fitted it up.
Needless to say, my customer was really happy to have his precious watch working again, and I was really happy to have made it happen!
I hope you enjoyed reading this as much as I enjoyed doing the work.
Until next time,
Blair.
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