I had some trouble this week trying to find the source of a faint grinding noise that occurred everytime I screwed the crown down in a particular watch I had just finished servicing and casing up. The movement would wind and set flawlessly when the crown was out, but as soon as the crown was screwed in a few turns the grinding noise would re-manifest itself.
Concerned that the problem lie in the keyless works, I wasn’t going to let the watch ship out without eliminating the cause. I wasn’t looking forward, though, to removing the hands and the dial – that I had just finished so meticulously polishing and ridding of dust – in order to find the problem. Fortunately, one of the more experienced watchmakers in the shop caught me with the watch held up close to my ear, in a last ditch effort to pinpoint the problem, and asked me what the trouble was. Once informed, he had the grinding noise remedied in about 15 seconds.
Turns out, the internal components of the new screwdown crown I had installed were binding. To fix the problem, he added a drop of lubrication to the shaft of the crown that rides in a spring loaded tube. Following that, he pumped the crown a few times, coaxing the light grease down into the base of the crown where the internal spring slides when the crown is being screwed onto the case. And just like that, the grinding was gone. Leaving behind nothing but silky, smooth, perfection.