Series of interconnected gears transmitting power from the mainspring to the escapement, regulating hand movement and watch functions with precision.
The gear train is the series of interconnected wheels and pinions that transmit power from the mainspring to the escapement, reducing the mainspring's high rotational speed to precise intervals for accurate timekeeping. It includes the center wheel (drives minute hand), third wheel, fourth wheel (drives seconds hand), and escape wheel.
Gear train precision is critical for accuracy. Any deviation in tooth profiles, pivot friction, or wheel spacing causes timekeeping errors. Jeweled bearings reduce friction at pivot points. The gear ratios must be exact: the center wheel completes one rotation per hour, fourth wheel per minute. Manufacturing tolerances must be incredibly tight (microns) for consistent performance.
Common issues include worn pivots from lack of lubrication, damaged teeth from impacts, magnetization affecting steel components, and dirt/debris causing friction. Regular servicing (every 5-7 years) prevents wear. Dropping a watch can bend pivots or crack jewels. Proper maintenance with specialized lubricants keeps the gear train running smoothly for decades.