The postings about key dip being fixed got me going.  Yes, it would make
sense to think that key dip or travel is fixed by the technician who
leveled the keys and dipped them.  However, this is not the true case.
I have had this pointed out to me in practice many times.

I have taught several young technicians to work on pianos.  The first
thing I have them do is to bush keys followed by easing, leveling the
keyboard, and, of course, dipping them thereafter.

Time and again I have had the apprentice level the keys and finish
dipping them.  Then I check everything to find not nearly enough dip
in any of the keys.  For the non-techs here, we dip keys by putting
a [slightly wedge-shaped] wooden or plastic block on one white key and
pushing the block down to the bottom of the key's travel.  The top of
this block should then be even with the top of the white key next to it.

I make a great point about making sure the block is pressed with only
the weight of the hand.  But often the novice pushes down into the felt
much harder than I do.

This means that the key dip when pushed with only the weight that
I apply normally will be 0.030" to 0.040" less than is proper.  It
usually takes some time for the apprentice to get the feel right for
dipping keys.  This is all compression of the front rail felt punchings.
This is why you must re-level and re-dip a keyboard after it has been
in use for a couple of years.  The felt gets compressed after a long
enough time and it compresses permanently.  It must then be adjusted
for that compression.

I know that when the pianist hits keys with enough force to get a
fortissimo (fff) there will a difference of 30-40 thousandths of key
dip.  I do not know if Welte used this on their recording piano or not.
I do not know how much difference there is between ppp and mf or
between mf and fff but I know there will be some.

D.L. Bullock    St. Louis
www.thepianoworld.com