[pianotech] boring, (was Hammer strike line)

[erwinspiano at aol.com]

   Hi Ed
  What do you find the average amount of over centering to be ie. no. of MM s the center of the hammer shank rises above the center pin height?
  Also I am most curious as to your subjective opoinion about what discernable differences in sound..if any? 
    uhhh...and the shank is parallel to what zzzzactly?
  Thanks Pal
   Dale






-----Original Message-----
From: Ed Foote <a440a at aol.com>
To: pianotech at ptg.org
Sent: Mon, Feb 8, 2010 7:51 pm
Subject: Re: [pianotech] boring, (was Hammer strike line)


Dale writes: 


 Perhaps the idea Ed was getting at was that whatever degree the string slope is that there should be a corresponding  amount of over centering and rake so the string and hammer are at right angles to each other ant the keybed. However this means calculating the slope on each piano or just checking it and averaging the bore. I think I just devised an A B Expereiment. I'll work on it



I do calculate the bore distance to the slope. I do this by using a set of graduated "hammers" glued up to shanks and flanges.  Actually, the "hammers" are various lengths of the Renner slats, glued to the shanks at exactly 90 degrees.  By putting, say, a 49 mm "hammer" in the piano, I can simply lift it to the string, drop a square down along its edge, and instantly see if it is at right angles to the string. When I find the correct length, I know that upon contact, the hammer is at 90 degrees to the string, and the shank is parallel.  It is quick, accurate, and easy.  
Regards,

Ed Foote RPT
http://www.uk-piano.org/edfoote/index.html
  
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