Tuning pin bushings

[Don Mannino]

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Dave Peake wrote:
>  
>>There is no practical reason for tuning pin bushings except for
appearance.
> For this reason I replace all of the bushings.<<
> 
Dave! You made a strong statement there. Sorry, but I have to disagree
with you.  There is a very good reason for tuning pin bushings in some
pianos - it all depends on how the piano is designed.  In some pianos
the bushings bear a substantial portion of the string tension.  Not the
tortional part of it (the pinblock keeps them from turning), but the
linear tension from the pull of the wire on the pin. In all bushed
plates the bushing assists in reducing the flex of the pin (which
affects the feel during tuning pretty substantially), but in Kawai
pianos (and some others) the bushing actually puts the string tension on
the plate webbing.  If you think about the benefits of having the string
pull being borne so close to the coil, I think the benefit in tuning
feel and stability can be understood. 

One of the best benefits of an exposed pinblock is that the coil is very
close to the surface of the block, reducing pin flex to the minimum.
The pin being shorter also reduces the twisting of the pin, make them
less prone to snapping. Many consider this to be the best feeling
design, but is generally considered too expensive when done well. That
could probably be overcome.

Sometimes it helps to think of the extremes.  Think about the last piano
you tuned which had tall tuning pins in an unbushed plate, with the
coils very high.  Now contrast that with the Kawai type or maybe a
Bechstein with an open pinblock.  They can all be stabilized well, but
very different tuning techniques are required.

If the bushings are replaced in a Kawai grand get them from Kawai, or
(when installing a new pinblock) cut your own plugs from rock maple or
pinblock stock . The best fit is obtained with a new pinblock by
installing plugs in the plate, then drilling the pinblock right through
the plugs.

If you are repinning a Kawai piano with oversized pins, the old bushings
can be left alone, as long as they aren't broken.

Don Mannino RPT
(Kawai Pianos)

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