Method for Correcting Watch Beat Error

       Watch beat error is also known as polarization, commonly referred to as a limping balance or tilted balance. By definition, "beat error" refers to when the balance wheel is stationary, the roller pin of the balance wheel deviates from the centreline of the escapement, thus causing the amplitudes of the balance wheel to the left and right to be inconsistent during oscillation—one side being larger and the other smaller—and listening to the ticking sound will also reveal a uneven beat.

       Watch beat error mainly affects the automatic starting performance of the watch. After the watch stops and is wound, it requires many turns of the mainspring before the watch can start moving; some even must rely on external shaking to start moving.  

       The roller pin (also known as the impulse pin) on the balance wheel must have a correct or precise installation orientation to ensure that the watch does not develop a beat error. During watch assembly, the double roller must have a positioning point, but this can only guarantee a rough position, and precise correction still relies on adjusting the hairspring orientation.

       The hairspring has an inner collet and an outer stud, which are the fixed points at the inner and outer ends of the hairspring. Adjusting either of them can cause the position of the roller pin to move. Mechanical watches in the early days featured "fixed outer studs" (including modern mechanical alarm clocks), meaning that the outer fixing point of the hairspring was made directly on the balance bridge and could not be moved. Therefore, back then, watches had many beat errors, and adjustments could only be made by removing the balance wheel and rotating the inner collet, which easily damaged the hairspring if not careful. The adjustment amount was also difficult to control, sometimes requiring repeated disassembly and reassembly to correct properly, which was very troublesome.

       Modern watches all feature movable outer studs, which can be rotated, making the correction of beat error very straightforward. Conversely, the inner collets of modern watches are basically triangular now, or even without a slot, and cannot be rotated, making them "fixed" instead. Adjustments typically rely on a timegrapher, observing the recorded lines or displayed milliseconds on the instrument to judge the degree of beat error. Without an instrument, one can rely on experience: in the stationary free state of the balance wheel, carefully observing the relative position of the pallet fork body allows one to determine the direction and adjustment amount for adjusting the outer stud.

       When the pallet fork body deviates to the left, the outer stud should be rotated anti-clockwise; when the pallet fork body deviates to the right, the outer stud should be rotated clockwise.

        When encountering vintage watches with a fixed stud holder, in my experience, rotating the double roller directly is preferable to adjusting the beat error, though this task requires careful handling.

        Just like the double roller, the hairspring also has a specific alignment position. Many watches feature a pinhead-sized mark on the surface of the balance wheel rim, which the stud should align with during hairspring assembly. If the beat error cannot be corrected within the maximum adjustment range of the movable stud holder, or if the regulator lever ends up extremely close to the second wheel after adjustment, the double roller will need to be rotated.  

        The adjustment sequence for a mechanical watch should begin with correcting beat error before fine-tuning accuracy; all adjustments must be performed when the watch is fully wound. Precision adjustments require extremely subtle, steady movements. Apart from watches with double swan-neck structures, stud holders generally do not feature micro-adjustment mechanisms like index levers. However, some high-end watches feature a locking clamp plate on the movable stud holder (for example, ROLEX 3135 calibres), requiring the clamp screw to be loosened before making adjustments.