Some of the steps in rebuilding an action
A piano’s action includes the hammers with their shanks and flanges, the whippens (consisting of all the other moving parts) and the action frame to which they are all attached. Action rebuilding ranges from replacement of hammers, shanks and flanges to replacement of all the parts and felts that make up the piano’s action. When an action is rebuilt, it is also regulated to make sure all the new parts function properly. New hammers are always voiced to ensure a tone that is consistent and pleasing to the piano player.
Jerry Raz, Piano Technician