<HTML>joegarrett@earthlink.net writes: <BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT= : 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">Also, there are times, for whatever reason is beyond me, the line from the butt flange<B= R> center pin is closer to the strings than Hammer bore distance dictates. </BL= OCKQUOTE> The reason I have heard for this is that the center of gravity is behind the= center pin, so gravity aids the hammer return. It may be properly called vertical pitch, but all the hammer makers I talk t= o at least recognize the term "rake." I confess that's what I use. Anyway, t= he center pin to string being shorter than the bore seems fairly common, so = it's needed to put the hammer head perpendicular to the string, or in the ca= se of some pianos like the older Steinways, a little overcentered. Shortenin= g the bore in order to cut the rake (excuse me, vertical pitch) changes rela= tionships between the jack and the butt. It might work and it might not, as = it would throw the butt forward and could cause the jack to skip out. Keith's original interest was in how to deduce the correct bore distance fro= m scratch, where the original hammers might or might not be present for evid= ence. I couldn't answer him right off at the meeting Monday, but upon reflec= tion, apart from looking at the rest position of the hammer rest rail with a= normal thickness of cushion, I would guess that the primary factor would be= the ability of the jack to push for the best power, and return efficiently = under the butt.  Bob Davis</HTML>