[CAUT] Baldwin SD (agraffe refurbishing)

[Overs Pianos]

Hello Mark and all,

>. . . How long does that nice crisp "hour-glass" profile last? IOW, 
>does the "V"
>shaped termination quickly become a "U" shape after a few tunings and some
>string-lifting?

With free-machining brass agraffes, the profile lasts about and until 
the piano is first chipped to pitch. We've experimented by 
pulling-out agraffes from a freshly chipped instrument. The profile 
is basically mangled at the outset.

This is why when using standard agraffes we'll get a couple of 
'zingers' as soon as the piano is tuned for the first time.

For some years we've been getting the agraffes plated with 
electroless nickel (which plates with a uniform thickness even inside 
the string holes) to a thickness of 2 thou' (0.05 mm). This was 
certainly helping the situation. Recently we've been getting 3 thou' 
plated to prevent the string from crashing through the hard plated 
surface into the soft brass beneath. The plating bath needs to be 
correctly balanced and continually filtered down to 1 micron with a 
minimum of 10 bath change-overs per hour, to ensure that a quality 
job is achieved with such a thick plating build.

EN nickel has an as plated hardness of just over 40 on the Rockwell C 
scale. It can be heat treated to around 60 Rockwell by heating it to 
260 degrees C for four hours. The mid phosphorus EN seems to give the 
best results with agraffe plating.

The piano we are bringing to Rochester in June will have EN plated 
and hardened agraffes, front duplex bars, mid section counterbearing 
metal profile, keyboard glide bolts and key capstans. EN is 
particularly suited to these high wear applications since it provides 
good corrosion resistance (much better than chrome), high hardness 
after heat treating and a friction coefficient which is around 70% 
lower than polished steel. In all its a wonderful process for piano 
manufacturing/rebuilding.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:ron at overspianos.com.au
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