Upright Piano Action Regulating

How to Remove the Upright Piano Action for Regulating

Align the jacks to the hammer butts.
After aligning the hammers with the strings, check the position of each jack under its hammer butt.

If the top end of a jack is off to one side, loosen the wippen flange screw and tilt the wippen sideways to center the jack under the butt; then retighten the screw.
In extreme cases, it may be necessary to paper one side of a wippen flange to bring the jack into alignment, but this also moves the front end of the wippen off to one side, which may be undesirable.