<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content="text/html; charset=iso-8859-1" = http-equiv=Content-Type> <META content="MSHTML 5.00.3105.105" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT size=2>Del,</FONT></DIV> <DIV><FONT size=2>Might want to mention that West does provide the = thickening material for changing viscosity. #403 Micofibers Adhesive is the name.</FONT></DIV> <DIV><FONT size=2>Tom Servinsky,RPT</FONT></DIV> <BLOCKQUOTE dir=ltr style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: = 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A href="mailto:pianobuilders@olynet.com" title=pianobuilders@olynet.com>Delwin D Fandrich</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = href="mailto:pianotech@ptg.org" title=pianotech@ptg.org>pianotech@ptg.org</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, September 01, = 2001 12:49 AM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: split bridge</DIV> <DIV><BR></DIV> <DIV><FONT color=#000080></FONT> </DIV> <BLOCKQUOTE dir=ltr style="BORDER-LEFT: #000080 2px solid; MARGIN-LEFT: 5px; = MARGIN-RIGHT: 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A href="mailto:davidlovepianos@earthlink.net" title=davidlovepianos@earthlink.net>David Love</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = href="mailto:pianotech@ptg.org" title=pianotech@ptg.org>pianotech@ptg.org</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> August 31, 2001 7:51 = PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: split = bridge</DIV> <DIV><BR></DIV> <DIV><FONT size=2>Joe:</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>Why would you not clamp epoxy?  The = bridge needs to be pulled back together, among other reasons, to get the = pins back in the right position.  My conversation this date with Roger Weisensteiner confirmed my belief that this would be the method = of choice for making this repair.  He suggested using a = two part epoxy (e.g. West System type) and clamp it back together reinserting = the pins either before or after it dried.  My concern with after is = that if I have to redrill the case might be in the way.  So I will = probably reinsert the pins before it = dries.</FONT></DIV></BLOCKQUOTE> <DIV dir=ltr><FONT color=#000080 size=2>Unlike nearly all other = adhesives, epoxy is an excellent gap filler. In fact, it actually requires a = rather thick glue line for best adhesive strength. Rather than say "don't clamp at = all," I would say clamp lightly--just enough to bring the crack just shy of = fully closed. </FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT color=#000080 size=2>West System is a good = epoxy for this repair, but it should be used with some kind of filler to improve its resistance to cold flowing--it is a plastic, after all. I would = suggest a bit of micro-fiber (ground cotton fibers) to add strength and some = colloidal silica to add hardness. Try equal amounts of each, adding just enough = to bring the matrix up to the consistency of warm peanut butter.</FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT color=#000080 size=2>You'll want to insert = the pins before the epoxy hardens. And you'll want to clean up the excess and = squeeze-out before it all fully hardens as well. Things can get pretty difficult = after the whole mess gets hard.</FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT size=2></FONT> </DIV> <BLOCKQUOTE dir=ltr style="BORDER-LEFT: #000080 2px solid; MARGIN-LEFT: 5px; = MARGIN-RIGHT: 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV><FONT size=2>Regarding solvents and epoxy, I have, in the = past, repinned bridges putting a drop or two of epoxy in the bottom of the = bridge pin hole prior to inserting the pin.  The squeeze out I have = cleaned up by brushing it onto the notch using an acid brush with a bit of = lacquer thinner.   I think I may have been introduced to this = technique by Bill Spurlock in a Journal article in fact.  Though I recognize = the controversy surrounding epoxying bridge pins in, I wasn't aware that = a bit of lacquer thinner was compromising the strength of the epoxy.  = </FONT></DIV></BLOCKQUOTE> <DIV dir=ltr><FONT color=#000080 size=2>Joe was referring to the = practice of adding a thinner such as lacquer thinner to the epoxy to thin it out = and get it to flow into the cracks more readily. It is true that you can thin = epoxy in this manner, but it does chemically weaken the material and introduces = a certain amount of shrinkage as the thinner flashes out of the mixture. = It is doubtful that you will get enough thinner into the epoxy mix using it = as you describe.</FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT color=#000080 size=2>Incidentally, epoxy = cures chemically, it does not "dry. It is this property that keeps it from shrinking as = it sets up. There is no--or at least, very little--solvent to flash = out.</FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT color=#000080 size=2>Regards,</FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT color=#000080 size=2>Del</FONT></DIV> <DIV dir=ltr><FONT = color=#000080></FONT> </DIV></BLOCKQUOTE></BODY></HTML>