<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=utf-8"> <META content="MSHTML 6.00.6000.16640" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT face=Arial size=2>Stephanie,</FONT></DIV> <DIV><FONT face=Arial size=2><STRONG>>The molding doesn't seem to have any parallel sides,<BR>and is asymmetrical of shape.</STRONG></FONT></DIV> <DIV><FONT face=Arial size=2>You should bore your hammers before doing your tapering or tail radius. If it's to late for that you will have to make spacers or come up with some way of making sure hammers always index the same in your jig.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2><STRONG>>Also, for those tenor and bass hammers who<BR>are bore with an angle, how do you calculate where the bit enters the<BR>molding, in order for it to come out at the back approximately in the middle<BR>of the molding (that is if you aim for that) ?</STRONG></FONT></DIV> <DIV><FONT face=Arial size=2>The first rule of hole drilling is always drill a test hole. Make some scrap pieces the same dimensions as your hammer moldings and drill them. Might not be too scientific, but it works.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2><STRONG>>I also experience problems in doing a dry fit : if it is tight enough, it is<BR>so difficult to move the hammer into its right position, while if it is easy<BR>to move the hammer, it won't stay in its right position after the first hit.<BR>Has someone found a solution for this dilemma ?</STRONG></FONT></DIV> <DIV><FONT face=Arial size=2><STRONG></STRONG></FONT> </DIV> <DIV><FONT face=Arial size=2>Try a little masking tape. Or put the shank in your mouth for 5 seconds and pretend it's a cigarette.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>I just hit on some of your more practical problems, as for the technical questions regarding how close is too close, depends on how hungry you are and what time is lunch. 1mm maybe, 2 mm maybe maybe not, 3 mm maybe not. I usually drill one or two different bore distances for the tenor through treble, I usually only drill one. I have drilled several in the same piano, this will result in having to consider multiple blow/dip relationships.</FONT></DIV> <DIV><FONT face=Arial size=2>Fenton</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2><BR> </DIV></FONT> <DIV><FONT face=Arial size=2></FONT> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A title=erwinspiano@aol.com href="mailto:erwinspiano@aol.com">erwinspiano@aol.com</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A title=pianotech@ptg.org href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, April 24, 2008 6:37 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: boring hammers</DIV> <DIV><BR></DIV><WBR> Dear Stephane<BR>  If you realize how much a millimeter difference can Make then be sure you bed the key frame first. Often the key frame is jacked up several mm's<BR>  Ask me how I know.<BR>  Dale<BR><BR><BR><BR> <DIV id=AOLMsgPart_0_98c306de-1240-4c2d-8d44-ae9f0a63cdda style="FONT-SIZE: 12px; MARGIN: 0px; COLOR: #000; FONT-FAMILY: Tahoma, Verdana, Arial, Sans-Serif; BACKGROUND-COLOR: #fff"><PRE style="FONT-SIZE: 9pt"><TT>Hi beloved list. I'm preparing to do another hammer change on an old piano, and I wanted to update my (poor limited) knowledge about good hammer bore practice. Up till now, I decided bore length from difference between strings height and center pin height in each section. I was surprised to see how far you can go off by doing those measurements, and how much one millimeter does count here. So I was happy to read about this wonderful shortcut which is to try in each section a dry fit of a hammer with known bore length, and see if it is perpendicular to string at contact time (really clever). This gave me also opportunity to ascertain that certainly in the treble, the string height can differ by one or even two millimeters depending on where precisely you measure it. Of course it should be at strike line, but again, how do you do that accurately ? Now, I have a few questions. How do you set up your boring jig in order to make sure that the hammer molding is perpendicular to the shank (that is, if you aim for that) ? The molding doesn't seem to have any parallel sides, and is asymmetrical of shape. Also, for those tenor and bass hammers who are bore with an angle, how do you calculate where the bit enters the molding, in order for it to come out at the back approximately in the middle of the molding (that is if you aim for that) ? Do you really adapt bore length at every section, or do you allow say one millimeter offset in uniformity's sake ? I read John D comment about the hammer shank length being fixed by design and so tweaking the hammer rake in order to get the perpendicular to string hit (if I got that right, John). In the ballpark that we play, is this really preferable to tweaking the hammer shank length and maintaining the 90 ° rake ? I also experience problems in doing a dry fit : if it is tight enough, it is so difficult to move the hammer into its right position, while if it is easy to move the hammer, it won't stay in its right position after the first hit. Has someone found a solution for this dilemma ? I have considered gluing the hammer simply like if it was to stay there, and then ungluing the usual way. But maybe there is another less demanding trick ? All advise welcome, of course. I'm mad about learning. Best regards. Stéphane Collin. </TT></PRE></DIV> <DIV class=aol_ad_footer id=u8CA748C1E003829-810-2322><FONT style="FONT: 10pt ARIAL, SAN-SERIF; COLOR: black"> <HR style="MARGIN-TOP: 10px"> Plan your next roadtrip with <A title=http://www.mapquest.com/?ncid=mpqmap00030000000004 href="http://www.mapquest.com/?ncid=mpqmap00030000000004" target=_blank>MapQuest.com</A>: America's #1 Mapping Site.</FONT> </DIV></BLOCKQUOTE></BODY></HTML>