A 'capstan' is an adjustable screw which is attached to the back of each key.
The capstan is the first point of contact from the key to the pianos action, thus putting everything else into motion.
Polishing or lubricating capstans is a standard part of our reconditioning process; a very important but often neglected task.
There are a few variations of capstans. Some are made from brass, others wood and plastic. It depends on the piano and which manufacturer made it.
Most capstans are made from brass, which over the years become tarnished. As photographed, the heads, on these 40 year old capstans, no longer have the same smooth surface that was originally polished into them when new, and now need 'freshening up'.
All brass capstans are polished to a high shine and capstans made from wood or plastic are lubricated, with a dry lubricant, as part of our standard reconditioning process.
Friction The reason that capstans are lubricated and/or polished, is to reduce friction between the head of the capstan and the heal of the action.
If the surface of the capstan is not adequately lubricated and/or polished, excessive static and kinetic friction occurs, resisting relative movement, which may cause your keyboard to feel heavier and harder to control.
Photographed, the same capstans after polishing.
Dry Lubricant The low-friction characteristics of specialist dry lubricants are attributed to a layered structure on the molecular level with weak bonding between layers. Such layers are able to slide relative to each other with minimal applied force, thus giving them their low friction properties.
As piano technicians, we understand the importance of eliminating as much friction as possible to maintain the desired touch and control. Lubrication and polishing is one of the many preventative measures we take against potential future wear and tear of friction points; making our instruments as long lasting and as low maintenance as possible for the future owners.