buzzing on piano

[A440A at aol.com]

<<  When the plate bolts were tigtened the buzz disappeared though for 
only 15
minutes.  (It came back as I was doing some regulation testing.)  I 
tightened the bolts
again and it was quieted for a short time. Tightening again (I put overly 
heavy torque
on this last time) lessened the buzz at F5 but it turned up at C6.   Soon 
the buzz
became strong at C6 and remained small at F5.  >>

Greetings, 
   First off, I would suggest stop tightening the rim bolts.  Next summer 
when the humidity goes up, the wood fibers around the threads will be crushed, 
and the bolts will be loose again. 
    It is possible that you have a loose dowel in the bridge.  Look carefully 
at the bridge and you will see a small hole or indication of where the dowels 
are.  They are blind into the bridge but you can see them all in the 
ribs,underneath, where the bridge crosses the rib.  By drilling a very small hole into 
the top of the bridge, into the top of the blind dowel, you can apply a very 
thin CA glue into the joint.  Sometimes the dowels did not go all the way up 
in the holes and there is a cavity formed that has a loose piece of glue in it. 
(I had this happen once).  
    It may not stop the buzz, but it will take one more variable out of the 
equation. 
Good luck,



Ed Foote RPT 
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html