Continuous overbanking, or knocking, occurs on a watch when when the watch’s balance wheel swing (amplitude) is too large. The watch’s escapement receives additional impact (roller/banking pin/pallet) with each balance swing and the watch is running, or appears to be running, very fast. While the cause of this can be incorrect escapement and beat error adjustment, modern quality watchmakers who completely disassemble and lubricate vintage watches with high quality modern oils encounter this issue more frequently than you might expect. This is because modern cleaning techniques and oils can cause a surprising number of vintage watches to run too energetically and overbank. Some watch calibers are more prone to overbanking than others due to their factory escapement design and margins. After adjustment causes and parts compatibility are ruled-out, the quality-focused watchmaker must then begin a search for a lower power compatible mainspring. This is done more efficiently by keeping a stock of mainsprings including ones no longer made. The watchmaker also needs to run through mathematical calculations and then proceed down a path of tedious testing until the best match is found. This all takes time and resources— correct quality servicing is not a “clean and oil” exercise— it’s a process of study, execution, and refinement. See a video of an overbanking watch, posted on the ClockSavant instagram account .
