During regular use, the felt products inside the piano action and piano keyboard wear. This is especially the case where the felt comes into contact with the wood and metal components found within the action and keyboard parts.
Here is a common repair done to the key set in many pianos; the replacement key bushings.
The keys in a piano are made of wood with holes mortised into the front underside and the approximate middle of the key. These holes in the key set are made to allow metal pins that act as guide pins keeping the key in a straight line while in use. So as not to cause noise during play, the mortised hole in the key set is fitted with a thin layer of hard-wearing felt that keeps the key motion correct. Over time these felt products wear and require replacement.
There are several ways to accomplish this task. This is one of the most popular ways of replacing key bushings. Please see the photo album at this link provided below.
Updated February 19 2013-02-19
In reality the aluminum cauls were designed for bushing replacement underneath the front of the key, as the shape of the caul will allow the cloth to be glued in an L shape.
When using the aluminum key bushing cauls, especially for the balance rail bushing replacement, this leaves a tail of bushing cloth that must be removed when the keyset is dry. That creates an extra step in the process of piano key bushing replacement and will lengthen the time required to complete a set of piano keys.
Many years ago, long before I was aware of the readymade bushing cauls, I used to make my own out of hardwood. For the bushing replacement at the balance rail, I have found these straight line cauls to work much faster as the bushing cloth can be cut off immediately after the bushing is set inside the key mortise.
I have included a few extra photos of my old wooden two- ended cauls at the end of the photo album attached to this posting.
Updated February 19 2013-02-19
In reality the aluminum cauls were designed for bushing replacement underneath the front of the key, as the shape of the caul will allow the cloth to be glued in an L shape.
When using the aluminum key bushing cauls, especially for the balance rail bushing replacement, this leaves a tail of bushing cloth that must be removed when the keyset is dry. That creates an extra step in the process of piano key bushing replacement and will lengthen the time required to complete a set of piano keys.
Many years ago, long before I was aware of the readymade bushing cauls, I used to make my own out of hardwood. For the bushing replacement at the balance rail, I have found these straight line cauls to work much faster as the bushing cloth can be cut off immediately after the bushing is set inside the key mortise.
I have included a few extra photos of my old wooden two- ended cauls at the end of the photo album attached to this posting.
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