To Jeff Bridges:  Assuming this is the studio sized Hardman Duo,
from the late fifties or early sixties, the tool required is called
a "drop screw regulator."  Any piano technician can obtain this
tool for you.

Also, the action stack height should be roughly regulated first,
by shimming it up on the ends where it rests in the piano.  This must
be done carefully to avoid damage to sensitive piano action parts.
Hope this helps.

Herb Lindahl
South Windsor, Connecticut