Hammer bore dimension

[David Love]

Vary the bore for each section.  Measure the first and last string
height in each section and bore accordingly.  You can line up the
hammers with the strike point flush and strike a line marking your bore
spot for each hammer.  The reason to vary the bore is so you get uniform
regulation, i.e. aftertouch with all else being equal.  I don't know if
this is a Steinway but I typically find that the plate dips on the
treble side and the bore dimension must gradually decrease at that end.
In the middle of the piano with only a 2 mm differential between high
and low, I might pick an average.  But, to be precise, bore for string
height variances.  

David Love
davidlovepianos@comcast.net 

-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On
Behalf Of Phillip Ford
Sent: Thursday, November 04, 2004 2:05 PM
To: pianotech@ptg.org
Subject: Hammer bore dimension

Since this is a political list now I'll attempt to keep this on 
topic.  Let's say that George Bush, in an attempt to make good on his
claim 
that "I'm a uniter, not a divider", hires John Kerry to rebuild his 
piano (assuming he has one).  John, in a spirit of bipartisanship,
decides 
to do the best job he can.  One of the things he decides to do is put on

some new hammers.  He measures string heights at several locations and 
hammer center heights.  He had planned to take the difference in these
two 
measurements and use this as the hammer bore dimension.  However, he
finds 
that the difference is not constant.  Here are some sample figures of
what 
he finds:

Note 21  Difference = 51 mm
Note 62  Difference = 53 mm
Note 88  Difference = 49 mm

What should John do?

1.  Use the same bore dimension on all hammers?  Why?  Which dimension 
should he use?

2.  Vary the bore from note 21 to note 88?  Why?

Phil Ford


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