[pianotech] problem in mating hammers to strings

[David Nereson]

I've encountered this several times now with grand pianos.  I 
level strings.  Then for each unison I hold the hammer up 
against the strings by pressing upward on the jack tender, and 
pluck the strings.  The ones that ring aren't being damped by 
the hammer.  The ones that don't ring are being damped, 
indicating (supposedly) that the hammer is "high" under that 
string.  Trouble is, I get the indication that all the hammers 
in the low tenor are high on the right.  Yet when tipping the 
front of the action up and viewing the strike points (which 
appear just above the flange screws from this vantage point), 
they appear straight across.
( _ _ _ _ _ _ _ _ _ _ )
    If I then file the right side of each hammer so that all 3 
strings of each unison are damped equally when holding the 
hammers against them, then look at them again from the front, 
they appear like the teeth of a giant rip saw  (|\  |\  |\  |\ 
|\  |\  |\  |\ , but imagine the line slanting to the right --  
the strike point-- slants only about a third as much as the 
backslash.)  But when I leveled strings, nothing told me that 
the right string of each unison was low, especially not that far 
low.
    This problem doesn't occur in the section with 
non-angle-bored  hammers nor in the capo sections.  So I'm 
wondering if, because of the angled hammers (not in line with 
the shank), the shank flexes when pressing up on the jack, 
causing the hammer to lean to the left, and giving me a false 
indication of how the top of the hammer is shaped.
    I've also had situations when, after spacing hammers, some 
of them still get thrown aside slightly on a hard blow, so that 
one unison string doesn't sound as loudly as the others.  In 
other words, the angle bore or something else is causing the 
hammer to travel or lean on a hard blow.
    --David Nereson, RPT