What is a watch winder?
Watch winder is a device with an electric motor to automatically wind up your watch when you are not wearing it. A winder keeps an automatic watch running and ready to wear any times. It also serves to keep the lubricating oil evenly and smoothly distributed even when you are not wearing your watch for a long period of time. A watch winder provides angular and/or circular motion that convert kinetic energy into stored micro electrical energy to keep the watch movement running. Watch winders are only useful if your watch is an "automatic" or "self-winding" watch; watches like Rolex, Patek Philippe, Piaget, Tag Heuer, etc. A quartz watch does not need a watch winder.
Why use watch winder?
In short, a watch winder serves 3 functions :
1. Provide convenience and time savings, and an ease of mind that your watch is ready to wear whenever you want, even if you do not wear the watch frequently;
2 Reduce an automatic watch's wear and tear, in particular to the crown winding mechanism;
3. Enhance mechanical life of the watches.
An automatic watch usually has sufficient power reserve to run for only a couple to a few days, depends on the brands and the movement it uses. If you do not wear it for a few days, the watch will stop and you need to reset it and rewind it again.
For watches with complicate functions like moon phase or perpetual calendars, to reset and to rewind it could be quite a tedious task that most watch owners would like to avoid. If you have more than one watch, to wind up and to reset each will not only be time consuming and tedious, but frequently resetting and rewinding the watch could cause certain harm to the mechanism of the watches; and could also hamper the long term mechanical life and functionality of the watch.
How can an automatic watch winder enhance the mechanical life of my automatic watch?
In addition to reducing wear and tear of the crown system as mentioned above, a properly designed watch winder can help distribute the lubricating oil inside the watch evenly most of the times. When a watch winds down and stops, the lubricating oil inside the watch will tend to settle and clot, and lose certain extent of its viscosity over an extended period of time.
As such, the chance of certain moving parts not being properly lubricated when the watch runs again is much greater. Resulting in increase friction and pressure caused to certain moving parts inside the watch. The consequence would be that the mechanical life of the watch could be shortened and the performance of the watch being hampered. This explain why certain watches, left in a watch retail store for too long a time without winding, seems to perform not in its pristine condition even if it is a "brand new" watch.
Can a watch winder "over-wind" my watch ?
No. Today's automatic watches are almost all manufactured with a mechanism that would dis-engage the winding mechanism once the mainspring is fully wind up. Thus, over-winding should not be a concern. But "over-stressing" should be considered when choosing a winder to wind up your watch. In particular when you use a "watch-spinner" instead of a real electronic programmed automatic watch winder.
In layman's term, over-stress is a result of placing an automatic watch in a winder that winds the watch non-stop, without any rest period in between. With this non-stop process, stress eventually build up. Like any other mechanical parts, over-stress could eventually shorten the useful life of the moving mechanism of a watch.