hammer bore distance

[Scott Nelson]

Hi David,
   
  I'm not quite clear on what you are saying about short hammer bore hammers "must start  with the shanks rotated upwards"  Are you talking about  the fact that the relative position of a short- bore hammer shank, being higher (more horizontal) than a longer bore would could result in a different touchweight? 
   
  Thanks, 
   
  Scott Nelson

David Love <davidlovepianos at comcast.net> wrote:
  I think you've already received adequate postings on this subject but I did
want to comment that you do see hammers on some pianos bored short and
compensated for with a rake outward so that the hammer is at 90 degrees to
the string on contact even if the shank is not parallel (pretty common on
older Bechsteins). Boring hammers on the long side so that the shank
doesn't reach parallel (except for small amounts in anticipation of wear) is
less common unless there is a problem with hammer/belly rail clearance in
the treble and strike point issues forcing the hammer to be raked in. Still
1/4" would be excessive. Aside for getting things square at the string,
boring them long also can create touchweight problems as it will set the
shank at a lower angle when at rest and can increase the effort required to
move the key at break away. Interestingly, short bored hammers that must
start with the shanks rotated upward will produce the opposite effect. 

David Love
davidlovepianos at comcast.net 
www.davidlovepianos.com

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Cal Munson
Sent: Monday, October 22, 2007 8:56 AM
To: pianotech at ptg.org
Subject: hammer bore distance

Hello List,

I have gotten some hammers bored recently and have discovered in 
putting them on that the bore distance is about 1/4 inch greater than 
on the old set. Using a let-off jig, a small level and a gauge to 
measure the string height, I checked my hunch and it appears that 
the bore is indeed 1/4 inch too much (shank does not get all the way 
up to perpendicular)

I am wondering what would be considered reasonable tolerances in 
the ideal bore distance?

Cal Munson




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