A watch movement must be regularly serviced in order to keep running properly over time.
As for a car, the movement must be maintained, and worn parts must be replaced.
Servicing starts with a visual inspection, in order to identify any obvious flaw.
The movement is then entirely taken appart.
All the parts are then cleaned using dedicated cleaning machines, the most delicate ones being placed in small separate baskets.
Each part is then closely inspected to identify potential signs of wear or damage.
Faulty parts are replaced with brand new ones and the movement is entirely reassembled. Precise spots must be oiled at various stages of the reassembly. Precise oiling allows to avoid any premature wearing of the parts, and participate in making the movement run smoothly.
Example of a movement dismounting, prior to cleaning.
Same movement during reassembly, after cleaning is done.
Timing of the movement is then adjusted, and several tests are performed to ensure the movement will remain as precise as possible in various situation.
The power reserve is also tested, to ensure it matches the manufacturer’s standards.
Finally, all the remaing parts of the watch are putted back together, and the final tests are performed.