The piano plate, sometimes called the frame or harp, is typically made from cast iron due to its high compression strength. The strings of the piano are attached to the plate in conjunction with the wooden frame and soundboard, and which the tension of the strings are supported. Many piano manufacturer’s use the O.S. Kelly company to supply them with piano plates. The company is based in Springfield, Ohio.
The cast iron is acoustically inert and is not readily reactive with other elements so it does not contribute to the sound production of the piano.
A crack or break in the pianos plate is a serious problem and requires special skills to repair, if even possible. A crack in the plate can greatly effect the tuning stability of the piano and could render it useless until a repair is attempted.
When restoring or rebuilding a piano getting correct plate position back into the instrument is crucial. Careful measurements are required before removing the plate from the piano so that proper installation back into the piano can be made.
