[pianotech] key leveling with a curve

John Delacour JD at Pianomaker.co.uk
Tue Oct 12 16:07:40 MDT 2010


At 17:01 -0400 12/10/2010, PAULREVENKOJONES at aol.com wrote:

>...I can see the argument for mimicking the string plane curve (maybe)...


Well, can you or can't you?  And if you can, how and why?  I can send 
you a few sample Steinway strike height curves if you like and you 
can tell us how on earth they can be mimicked in the key levels.

The way I understand it (and I too am open to correction) is that the 
key bottom (sic, NOT 'key bed') of the Steinway is arched at the 
front (only), being one millimetre higher in the middle.  When the 
key blocks are screwed down, the front rail is bent to follow this 
very slight curvature and to press closely against the key bottom so 
that there can be no knocking of the front rail against the key 
bottom.  The keys are raised to follow this curve and, in an ideal 
case, the total thickness of the punchings required under the front 
baizes will be the same throughout the scale.

JD



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