Action Rebuilding involves stripping your action of all its old parts
and replacing with brand new parts. The most obvious reasons to rebuild
your piano's action are broken parts and worn out felt and leather.
While it is not unusual for an occasional part to break, multiple examples
of the same part breaking means it is time to replace all of the parts.
As hammer felt ages it will develop deep grooves, turn yellow and lose all
of its resiliency and elasticity. It ceases to be a flexible, springy hammer,
becoming a hard non-flexible mallet. The keyboard felt and leather is subject
to moth damage as well as being worn by friction from decades of use, becoming
noisy and loose. Long before any of this has happened though, the performance,
both mechanically and musically, of the action has deteriorated. It may work and
make a sound but not like it should.