[pianotech] boring, (was Hammer strike line)

Ed Foote a440a at aol.com
Mon Feb 8 12:17:25 MST 2010


 
 
Dale writes: 
Original hammers and shanks over centered a good bit. Ourshop does not do it this way. My formula is :String height minus center pinheight minus 1 mm in each section. 


I said, 

This will place the hammer at right angles to the string uponcontact ONLY when the string plane is parallel to the keybed. What do you do when there is a considerable rise of the strings from the capoto the bridge? 
 

David asks: 




>>Why is that?  Wouldn’t subtracting the 1 mm compensatefor some rise in the string toward the bridge?  
  



I don't know, that would depend on the actual angle of the rise, and if it does, then it sets all the other sections out of square, no? and if the strings are parallel, the missing 1 mm will cause over-centering at the beginning of the hammers' life.   

  I have seen quite a few pianos with a very sharp rise to the bridge. In those cases, new hammers bored short enough to create the 90 degree match to string would have been too short to regulate properly,(shanks way off the rests).  It is sometimes necessary to hang the top section with an acute angle to the hammer, plus boring a short as possible. 

Regards, 

Ed Foote 


 
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