Creating smoother travel between the piano key assembly & key bed
The una corda pedal (or, "the soft pedal") on a grand piano, is used to move the entire key assembly ("action assembly") to the right of the piano, allowing the piano hammers to hit the piano strings in a different position than at the resting position, causing a more muted or "softer" sound. For example, with the una corda pedal depressed, the hammer on a single string note will hit on a softer part of the hammer, if the hammer is voiced properly. As well, with the una corda piano pedal depressed, on a bi-chord note, the hammer should only hit one of the two piano strings and on a tri-chord note, the hammer should only hit on two of the three piano strings, causing less sound during each strike of the hammer against the piano strings. Sometimes, the area between the action assembly and the key bed on a grand piano, which is the area directly beneath the piano keys, will have rough terrain, which causes friction, as well as undesirable noises when the una corda pedal is depressed.
During this repair, we first remove the piano fallboard. Then, we remove the cheek blocks and then the entire action assembly from the grand piano. Once the action assembly has been removed, we use 400 to 600 grit sandpaper to sand down the bottom of the action assembly in all areas where the action assembly regularly meets the key bed. As well, we use 400 to 600 grit sandpaper to sand down the key bed, where the action assembly rests and travels upon, while in the piano. Once we have finished sanding down those areas, we simply vacuum the dust created by the sanding process and then add teflon powder to any area where the action assembly rests and travels in the key bed once the una corda pedal is depressed. We then reset the action, cheek blocks, key slip and piano fallboard. Once complete, we test the progress by depressing the una corda pedal to compare the difference in movement and travel from before we began the repair process. The piano's action assembly should move much easier and smoother as a result.
In the following video, piano technician, Joel Lane, is in one our piano storage & repair buildings and shows us how he creates smoother travel between the grand piano's action assembly and the piano key bed, allowing for cleaner and softer movement when depressing the una corda pedal.
At AAA Piano, we offer in-home piano repair as well as provide piano repairs in our piano storage & repair shop in El Dorado Hills, California. Give us a call for a quote on your piano repair, or with any questions you may have, regarding your piano:
-Joel Lane, AAA Piano