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<DIV><FONT face=Arial>You want to measure the angular relationship of =
the string
in three areas: along the speaking length; along the bridge top; and =
along the
backscale just aft of the rear bridge pin. Those measurements will give =
you all
the data you need to characterize downbearing.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Be aware that all these references to setting =
bearing to
"the thickness of a nickel" or whatever level above some reference point =
may be
fine and dandy, but are completely dependent on the length of the =
backscale. As
the backscale length between two systems where this type of measurement =
is being
used varies, inaccuracies in the reference thickness will be
introduced.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>How much downbearing is desirable will depend on =
the
soundboard assembly design, where you are in the scale, and a host of =
other
factors I know very little about!</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Terry Farrell</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>
<A title=Crashvalve@aol.com
href="mailto:Crashvalve@aol.com">Crashvalve@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> Monday, October 06, 2003 =
7:38
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Good at Machining =
WAS:
Reading a Board geometry</DIV>
<DIV><BR></DIV><FONT face=arial,helvetica><FONT face=Geneva =
color=#000000
size=2 FAMILY="SANSSERIF"><BR>In a message dated 10/6/03 12:54:05 =
AM, <A
href="mailto:yardbird@vermontel.net">yardbird@vermontel.net</A>
writes:<BR><BR><BR>
<BLOCKQUOTE
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solid; MARGIN-RIGHT: 0px"
cite="" TYPE="CITE"></FONT><FONT face=Geneva color=#000000 =
size=2
FAMILY="SANSSERIF">I'm assuming you've got some sort of milling =
machine, not
necessarily<BR>a Bridgeport. I bet you could do a good job of making =
a
component<BR>downbearing gauge, the one with the adjustable =
inclination
bubble<BR>mount. Someone send this guy a .jpg of one (not
necessarily<BR>identifying its maker).<BR><BR>Bill Ballard RPT<BR>NH =
Chapter, P.T.G.<BR><BR></BLOCKQUOTE></FONT><FONT face=Geneva =
color=#000000
size=2 FAMILY="SANSSERIF"><BR><BR>Living near Detroit I have =
acquired lots of
machinery from old tool and die shops. To do credible work you need =
both a
mill and a lathe and a lot of support tooling. Can be a time waster in =
that
one of three experiments is good to go. Re the downbearing gauge I =
bought one
from one of the suppliers years ago and returned it because of the low =
precision bubble vial. Your best bet would be a simple jig with a =
place to
temp. mount a machinist's level. A good one is accurate to .005 per =
foot and a
REALLY good one goes .0005 per foot. Question is (and this goes back =
to the
vector discussion in recent threads) what do you want to measure, =
which two
surfaces to you want to relate to each other ? Even S&S once =
specified
thickness of a NEW coin for down bearing gauging, or was that just =
romantical
hype ?</FONT><FONT face=Geneva color=#000000 size=2 =
FAMILY="SANSSERIF"></FONT>
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