Reconditioning
Key Rebushing
Each key on a piano is held in place by two pins: the balance rail pin near the center of the length of the key, and the front rail pin which holds the key in place at the front. There is a hole near the middle of the key through which the balance rail pin goes, and there is a hole in the underside of the front of each key which fits over the front rail pin. Each of the holes is "bushed" with thin felt. When the piano is new, the bushings are loose enough to allow the key to move freely up and down, but tight enough so that there is no sideways movement of the key.
After the piano has been played a lot, the felt bushings become worn and compressed, and the keys get what I call "woogedy woogedy" - they wobble from side to side, sometimes so much that they click and knock against neighboring keys. This gives the pianist a very insecure feeling, and causes a loss of power since not all of the energy is going downward.
[The photos below show the rebushing of front rail holes. The same process is used for rebushing balance rail holes.]
In the photo below, note the indentations the pins have left in the felt. There is one bushing that is missing completely.
The proper way to correct worn keybushings is to replace the felt bushings. This must be done extremely precisely. First the old bushings must be removed by steaming them and lifting them out.
Next, the right thickness of felt must be determined to assure the proper fit for the size of pin that will be going into it. Hot hide glue is put on the felt, and it is held in place with special cauls. The edges of the felt must be trimmed carefully so no felt is left poking up, since this would throw off the regulation of the key dip when the keys are back in the piano.
After the glue has dried, the cauls are removed. If the rebushing has been well done, very little adjustment (easing) of the bushings will be needed when the keys are put back into the piano.
