Key let up - knocky noise

[Mike Erickson]

Although there are plenty of piano tooners of lower caliber than I, I
am still ashamed to admit, after a full year of training, fourteen years
of piano servicing, and sitting through more Grand Regulation Seminar
classes than I can remember, -> that I still have "grand action phobia".
Coming out of those classes does help me to face my fears, and I usually
understand one more small tidbit after each class,    But like
tuning..., it takes experience on hundreds of different pianos until you
realize the potentials and limits that "tuning" can bring to each make,
model, age, and condition of piano.     "Is it me? the voicing ? poorly
designed instrument?"  Now, after thousands of tunings I am confident I
have a good sense about what can or cannot be improved in the tuning,
and somewhat with voicing and upright regulation. I don't, however, have
such a great sense when it comes to grand actions.  It's mostly a hate
relationship at this point. I would hate to sell a job to a customer,
struggle for days on the action, ask for help, only to find that it is a
hopeless cause or that my efforts have made things worse. That is why
when there is 
big-big trouble in a grand action, I usually refer the job to local
technicians who have immersed themselves in grand action servicing
and/or rebuilding. Maybe I'll quit tiptoeing and really fall into it
someday.  Until then, thanks for listening and I will humbly ask my
stupid symptomatic questions about the mysteries I encounter. 
   Question # 1, encountered 10/7/97, 35% realive humidity, a 1965
Steinway L, teflon bushed.  
When the key is let go, on the up stroke, there is a woody knocky sound.
I perceive the sound at a dull level throughout the action, which is
acceptable or at least bearable, but I percieved the knock at  an
obnoxious volume on several notes, mostly in the midrange of the piano.
Hoping I could help this by some flange tightening, I found all flanges
to be tight. Hammer heads - tight. Although balance rail bushings seem
overeased, when the key was held securely, the same "knock" was heard
when dropping the hammer down onto the rep lever. 
I thought, maybe the shank was hitting "tapping" the top of rep lever
height adjustment screw head, but when I held a piece of bushing cloth
inbetween - still no improvement.  The "shank cushion?" is plenty soft.  
  After 48 minutes of trying to isolate the cause, I gave up. I smiled
at the customer, told her I was "exploring" (although didn't tell her
why or what for, since she hadn't complained of anything) and, of
course, charged her no extra for my venture.
  I only service 6 other Steinways, so I'm not sure if this woody knock
noise is native to telfon Steinways or all grands. 
I don't remember the other times I have encountered this and cannot make
the connection. Any ideas?  Any help appreciated !

Mike Erickson,  Tucson, AZ    mwike@flash.net