balance hole reamer?

[A440A at aol.com]

 JD writes:

<< Yes.  Now answer me this :  The picture below shows keys from grand 
pianos by three excellent makers.  In all of them the lowest contact 
with the balance pin is made over 1mm from the bottom suface of the 
key. Why? >>

I would assume that it is to prevent wood from splitting at the edges of the 
hole. And it seems that if you push a conical burnisher in from the bottom, 
you are raising the contact edge even higher up in the hole. 
Regards, 
Ed Foote RPT 
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html
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