<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=US-ASCII"> <META content="MSHTML 6.00.2900.2963" name=GENERATOR></HEAD> <BODY id=role_body style="FONT-SIZE: 10pt; COLOR: #000000; FONT-FAMILY: Arial" bottomMargin=7 leftMargin=7 topMargin=7 rightMargin=7><FONT id=role_document face=Arial color=#000000 size=2> <DIV> <DIV><FONT style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2> Hey JD</FONT></DIV><FONT style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2></FONT></DIV> <DIV><FONT style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2> <DIV><BR>>When boring hammers, should we favor strictly the string heigth <BR>>minus shank center heigth at the cost of no straight hammer heigth <BR>>at rest (reflecting the not straight strike line heigth at strings) ?</DIV> <DIV><BR>JD wrote<BR>Broadly speaking I agree with Dale Erwin, as far as he goes, except <BR>that I aim to have each hammer strike the string at exactly a right <BR>angle.  I don't follow the reasoning as regards over-centring.</DIV> <DIV> </DIV> <DIV><STRONG><EM>The logic you share should indicate an error in the approach you suggest.  Since the strings and key bed are not parallel to each other a hammer mounted at right angle to the shank is going favor hitting the back side of the hammer striking point. Also altering the bore distance by making it longer changes the geometry of the entire action as the capstan & every other reg screw need to be turned downward. </EM></STRONG></DIV> <DIV><STRONG><EM>    Some tech's even allow for the anticipated wear of the hammer adding a mm or 2 to the bore length.  This is huge design error in my opinion.  Having run across pianos with this configuration I can tell you they do not play well.</EM></STRONG></DIV> <DIV><STRONG><EM>  IMO a new set of hammers bored & hung in the correct place to the string plane as I described will tolerate only one heavy filing before the action is no longer in it's optimal geometric performance range & over boring isn't a remedy for this,  a new set of hammers is</EM></STRONG></DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV> It <BR>might be argued that the shank bends under a heavy blow and therefore <BR>tends to cause the hammer head to under-centre slightly, but given <BR>the rigidity and thickness of modern shanks, particularly the <BR>hornbeam ones, I doubt if this is significant and would need to see a <BR>slow motion movie to be convinced.  Nevertheless I think it would be <BR>a valid research exercise for someone with the equipment, if it <BR>hasn't already been done.</DIV> <DIV> </DIV> <DIV>  <STRONG><EM>Actually I believe the Kimball video shows the shank bending</EM></STRONG><BR><BR>Let me re-emphasise the importance of taking into account the slope <BR>of the strings, which is considerable, and most critical, in the high <BR>treble -- but this slope needs to be measured throughout the scale <BR>for every piano and factored into the bore angle.  If this is <BR>ignored, the hammers in the extreme treble will under-centre.</DIV> <DIV>  <STRONG><EM>Exactly where I'm coming from<BR></EM></STRONG><BR><BR>Aesthetics is a broad concept and applies to function and design in <BR>all its aspects.  There is nothing intrinsically beautiful about a <BR>straight line, as any  ancient Greek architect could tell you.  Is a <BR>clothes-line or a telegraph wire intrinsically ugly? :-)</DIV> <DIV> <FONT size=4><STRONG><EM> Now we agree on that!!</EM></STRONG></FONT></DIV> <DIV><EM><FONT size=4><STRONG>  </STRONG></FONT><FONT size=3>Dale</FONT></EM><BR><BR>JD<BR></DIV></FONT></DIV> <DIV></DIV> <DIV> </DIV></FONT></BODY></HTML>