i have a Kawai grand piano that has undergone radical transformations over several years.
after several reweightings, the keys have lost almost all of the original factory lead weights inserted inside the key itself; furthermore (also due to various reweightings done at different times), many extra holes have been added, most of which are now empty. The keys resemble a colander, they are full of holes.
The technician recommends restoring the action with original measurements, filling all the holes with wood, and finally re-drilling to perform a further weighting of the keyboard. An important intervention nonetheless.
I think it was inadequate work. At the very least, when the new hammer rail requires a new precise balancing, one must use the same holes with weights of the same diameter but different thickness. In any case, now it is necessary to return to the original hammer rail and absolutely plug the holes with spruce dowels of the same diameter. The holes must not be left empty. Otherwise, there is a risk of weakening the keys and the possibility of fracture and/or increased vibrations during heavy depression. Attention: before "re-weighing and re-drilling," check THE FRICTION: Never try to balance a false excess of downward weight with an increase in weighting. This will do nothing but make things worse. Another sign: one key and the next should not have sudden changes in weighting.
