Good evening everyone, I hope I have posted in the appropriate section this time. I wanted to open a discussion by proposing an issue that is, in my opinion, rather thorny. Regarding the keyboard leveling of an upright piano, I don't have any problems whatsoever since it is possible to modify the level with the weight of the action that rests directly on the key, removing the key as needed. For a grand piano, the matter becomes more complicated. I am trying to level the keyboard of my Yamaha C3 at 64mm, but I am encountering the problem that I will now explain. I proceeded in the following way: first, I measured the distance from the keybed of some sample keys... some were 64, some were slightly out of alignment. The interesting thing is that when I removed the keyboard action, placed it on the workbench, and measured the distance from the wippen to the surface of the bench, almost all the measurements were off by about 1mm (further away). I assume this is due to the irregularities of that specific keybed, which are difficult to reproduce on another support. At this point, I disassembled the action and removed most of the keys, leaving only 3 or 4 reference keys for the various sections. I then applied specific weights to the hammer regulating levers to simulate the weight of the action, but even this time the resulting distance was imprecise: I applied 90g weights to the bass keys and found that the distance became even greater compared to what was measured with the action assembled on the workbench. To get the same measurement (anyway 1mm more than the key-to-keybed distance), I had to go down to 40g per key (in the bass). In essence, I have no reference points to perform a precision adjustment because the distance I detect on the workbench does not exactly correspond to what I measure once the action is placed in the piano. Besides this, the use of weights was unsuccessful since I am detecting a third measurement, which doesn't even correspond to what I find with the action assembled on the workbench.
How do you proceed in these cases to perform an adjustment that is not coarse, but precise? Should I perform the measurement on the workbench considering the 1mm discrepancy? Is it better to level a grand piano directly on the instrument? But if so, how? Help
