Whether you are practicing regulation on an upright model or trying to set key height on an older piano with no manufacturer’s spec, an important skill to acquire is being able to set key height based on the piano’s case parts.
For the purpose of the article, we will be demonstrating on a three-note action model, but the procedures and theories apply to upright and grand pianos.
There are several factors you should observe when setting key height. To set key height on an action model, you should work on one sample white key first. Remove all paper punchings from the balance rail pins. Reinstall the white key with only the felt punching and observe the height of the balance rail pin in relation to the top of the key mortise. It is important to select a key height that will allow the balance rail pin to have ample height over the top of the key. Pins that are buried in key mortises will cause many problems in regulation, including wobbly keys. Your balance rail pins should never look like this:
A good balance rail pin height should look similar to this:
Add some paper punchings under the felt punchings until you are comfortable with the appearance of the balance rail pins. Now, you should observe the key in relation to the keyslip. Proper key travel should end before the overhang of the key hits the keyslip. Conversely, the key should not be so high that you are able to see the edge of the key with the keyslip installed.
Once you have set key height to the balance rail pins and keyslip, install the keystop rail as a final check. If key height is too high, the keyslip may press the keys down once it is installed. You may be able to see this happening as you tighten the key rail. If you are unsure, push the key up with your finger to get a feel for the clearance between the key and key stop rail. Good spacing should be about 1/16” lift before the key hits the key stop rail. If the keys are too high, there could be no space between the key and rail.
If key height is too low, there will be excess clearance between the rail and top of the key.
Now you can install the black key. Regulate black key height so that it is 12.5mm (or ½”) above the white keys. You can use digital calipers or a ruler for this: