Unlike large clocks, there is no room in a small mechanical watch for an over designed mainspring and a very small mainspring will only deliver a very small amount of driving power. To enable a watch to run with so little power, the bearing pivots are extremely fine and in a good quality watch, run in jeweled bearings, oiled with the finest quality synthetic watch oils.

Nevertheless, in such a fine and precisely built mechanism, a microscopic speck of dust, floating in a tiny oil reservoir can come into contact with a pivot and stop the watch. Consequently, it is necessary for a watch to be serviced more often than the average clock. Every two or three years is recommended.

Quartz watches also require servicing in exactly the same way as mechanical watches. The difference in a quartz watch is that instead of a mainspring driving the watch, there is a battery and instead of a balance wheel and hairspring oscillating at eighteen thousand times an hour, there is a quartz resonator oscillating at many thousand times a second and a step motor operating through a micro chip to drive the hands. But, beyond the step motor, there is a train of wheels or gears exactly the same as any mechanical watch, but with even less power than a mainspring driving them.