<!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 5.00.2919.6307" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV>"When a wood flange swells with high humidity the action center = hole swells also, more so with the grain than across the grain.  Think of it = this way: when you have a hole in a normal (non-laminated) piece of wood, the hole = behaves like the plug of wood which was removed.  With a large humidity = increase, action center holes in the wood get slightly oval if they were drilled = when the wood was very dry."</DIV> <DIV><BR>I have heard/read this many times, so I suppose it is true. = But, intuitively, it makes no sense to me. If you drill a hole in a piece of = wood and expose it to high humidity, the wood will swell - and swell much more = across the grain (perpendicular to the grain direction) than with the grain. So why = doesn't the hole tend to close a bit - on the two sides of the whole = where the tangents are parallel to the wood grain.</DIV> <DIV> </DIV> <DIV>If I take a board, drill a half-inch diameter hole through it, push = a half-inch diameter rod through it (snug fit), and place the board in = water or high humidity, I should think the rod would be tight in the wood - maybe = even crack it (meaning of course that the hole gets smaller with increasing humidity). And if dried in a kiln or real low humidity environment, = wouldn't the rod just fall out? I suppose I need to get a board and rod, but typing = is easier - unless of course you don't agree with me! :-)  Maybe then I'll = have to do the field test.</DIV> <DIV> </DIV> <DIV>Where is the flaw in my reasoning? (I hope this post doesn't sound = snotty - I'm trying to understand - you see, you can't see the inquisitive look = on my face and the absence of a know-it-all look!)</DIV> <DIV> </DIV> <DIV>Terry Farrell<BR>Piano Tuning & Service<BR>Tampa, Florida<BR><A = href="mailto:mfarrel2@tampabay.rr.com">mfarrel2@tampabay.rr.com</A></DI= V> <BLOCKQUOTE 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:DonMannino@mediaone.net" = title=DonMannino@mediaone.net>Donald Mannino</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> Sunday, December 31, 2000 = 11:35 AM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: moisture in wool = or wood.</DIV> <DIV><BR></DIV><FONT size=3>Hi Gang!<BR><BR>I guess I should chime = in on this topic, as I've played around with action centers quite a = bit.<BR><BR>The wool cloth swells a lot with moisture changes.  This is the main = reason action centers are so hard to manufacture so that they work in all = climates.  You will find that the most reliable action companies make the centers = seem rather loose if you are in a dry climate.  They do it that way so = that it will still work in humid climates.  To really be reliable in = Florida and Southern Texas, they need to be on the edge of too loose in Alberta!<BR><BR>When a wood flange swells with high humidity the = action center hole swells also, more so with the grain than across the grain.  = Think of it this way: when you have a hole in a normal (non-laminated) piece of = wood, the hole behaves like the plug of wood which was removed.  With a = large humidity increase, action center holes in the wood get slightly oval = if they were drilled when the wood was very dry.  Since the hole is so = small, though, this effect is pretty slight.<BR><BR>The wool fibers swell in = all directions, but the cloth sheet swells in the direction that is = easiest to move.  If you wet a piece of wool cloth laying out on a table, it = will get a lot thicker and a little smaller in width and length.  Then = it will generally stay there after it dries.  <BR><BR>If you submerge a = hammer in water, it's reaction will depend on how tightly bound together the = fibers are.  Soft hammers will bloom out into a fuzzy ball, while very = hard hammers will hardly change shape at all.  I once soaked a really = nasty hard sample hammer in a glass of water for a week, and after it dried = out it sounded pretty good!<BR><BR>If you wet wool cloth and place a weight = on it, it will swell up slightly and try to lift the weight, then it will shrink = back down and (if the weight was heavy enough) the cloth will end up a = little thinner than it was before.  Similarly, if you put a hammer into = a hammer press and add steam, the hammer will get smaller and harder.  = This is how alcohol and water works to loosen a flange bushing.  Because the = bushing is bound up by the pin and flange, the fibers try to swell with the = moisture (the water does the work, the alcohol is sort of a "thinner" and = penetrating agent).  They get squeezed more tightly together and pack the = fibers more tightly together, sometimes squeezing out the sides a little! Then = when they dry again, the bushing is thinner and works more freely.<BR><BR>Sizing = doesn't work as well after a certain point, as the wool becomes packed as = tightly as it practically can.  If the original cloth was kind of cheap, wet = sizing with alcohol and water gives great results, if a bit = inconsistent.<BR><BR>In theory, action centers in wood parts _should_ react less to humidity = changes than plastic parts do, but in reality the difference is so slight as = to not be measurable consistently.  I have done some experiments comparing = the changes in center pin friction with extreme humidity changes, and = sometimes I found slight differences in the change between wood and plastic.  = In other tests, I couldn't find any differences, so the tests were just inconclusive.<BR><BR>If you want to do some testing yourself, be sure = to rebush all flanges with the same cloth before you start, so that you = eliminate different cloths and pins as variables.<BR><BR>Keep in mind that = humidity is only one reason that action centers get sluggish.  In my action = center class I talk about all the different reasons that centers go tight, = and there is a pretty good list.  Cloth which was not originally glued into = the flange in a stable position is one common reason (twisted cloth), as = are burrs on the pins.<BR><BR>Don Mannino = RPT<BR></BLOCKQUOTE></FONT></BODY></HTML>