Piotr Barcz is asking some interesting questions about key dip and
hammer blow distance. My friend Richard Friedman already has offered
some solid advice on the subject. I like to say that a piano action
is an amplifier of sorts in that the key is depressed 3/8" and the
hammer travels 1-3/4" or so.

I, too, have found pianos to have hammers travelling well beyond the
recommended 1-3/4". When I replace hammers I generally set them around
1-3/4" or maybe a touch more by adjusting the felts that the hammer
rail rests on.

With respect to key dip I will share that it is not so much important
to set the dip at 3/8" (which, incidentally, never feels good), but to
observe the function of the hammer action through the escapement cycle
and its performance most notable at the check point.

The key dip should be such that under light touch (depressing the key
until it contacts the front punching without compressing it) that the
hammer checks and has a good solid catch by the backcheck. If it is
too shallow the hammer will bobble, if it is too deep the hammer will
be forced forward by the back check.

Richard correctly notes that this will generally yield a key dip
around 13/32". The check distance is good around 3/4"; if you must
bend the back wires to get that distance then it is highly likely
that the dip is too much.

Before making these adjustments be sure the lost motion has been
taken out: the jacks are checking uniformly releasing the hammers when
they get close to the strings. It is recommended that they check right
up close to the string but I do it so they check a little sooner --
it helps with soft playing, it seems to me.

Another super-important regulation for pianos is the point at which the
dampers begin to lift. I find that the dampers often are starting to
lift way too soon in the escapement cycle. Player pianos sound better
when they begin their lift fairly late in the hammer stroke; the piano
will sound cleaner this way.

These comments apply equally to grand and upright piano actions.

Happy regulating!

Ben Gottfried - Ben's Player Piano Service
Richfield Springs, New York
https://bensplayerservice.com/