Bridge pin angle

[David Love]

I agree.  The real issue is how to get the pin solid (or how to prevent
it from getting unsolid) and, also, how to prepare the cap.  I am,
admittedly, rethinking my approach in all this.  On new bridge caps
(since I don't have a notcher and don't use delignit) I am getting into
the habit of coating the top and notches with a clear coat of epoxy
prior to pinning.  I use the System Three thin stuff for this.  Clean
out the holes with a toothpick to insure no buildup. Then, when fully
cured sand it back down smooth without going below the original level.
The epoxy on the cap and on the notches seems to harden and support the
edge a bit and help prevent string indentation and damage.  When it
comes time to insert the pins I swab the inside of the hole with just a
bit of clear coat epoxy (very thin using a toothpick) and drive the pin.
Not so much that I get any or much squeeze out, but enough to secure the
pin.  I wipe away any excess as I go.  Afterward, I don't file them flat
as I see no reason to stress the pin/cap joint by pushing back and forth
and heating them up with the file.  When all is complete, I mask off the
board and shoot a very light coat of satin lacquer over the whole thing
for appearance.  

While the tradition has been to be sure the notch edge is a sharp edge,
I have begun to wonder whether or not a slightly rounded edge wouldn't
be better.  Since the critical point of termination is the pin and not
the edge of the cap, just the slightest rounding back to the edge of the
bridge pin itself would seem to prevent a slight amount of compression
from creating a bridge surface that extends beyond the center of the pin
out into the speaking length.  In terms of seating the string, I'm
finding that the most effective seating is done with a slight push on
the string toward the bridge pin rather than down on the cap.  Much like
massaging the strings up on the capo bar, settling the string onto the
pin itself seems to be more effective.  This is, of course, assuming (as
you mention, Ron) that the bridge pin is secure.    

David Love
davidlovepianos@comcast.net 

-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On
Behalf Of Ron Nossaman
Sent: Thursday, April 28, 2005 5:03 PM
To: Pianotech
Subject: Re: Bridge pin angle


> I've not really been following this discussion in all its detail so
this
> may be an already expressed opinion but here's what I see happening.
> Under any conditions, with sufficiently angled bridge pin that is
> unnotched, there is no way for the string to ride up the pin--period.
> But as the bridge top expands and contracts the edge of the bridge
> becomes indented more than the top of the bridge because of the
> squeezing with changes in humidity against the bridge pin.  Now when
the
> bridge shrinks the line of the indentation at the edge of the bridge
> will not be on the same plane as the top of the bridge.  Because of
the
> stiffness of the string and its tendency to want to stay on the plane
> formed by the top of the bridge, the deeper indentation at the edge of
> the bridge can cause a gap to form underneath the string at that
point.
> Tapping down the string will cause the string to move, but it is a
> temporary measure.  The string will want to regain it's original shape
> and position.  Over time, and not probably very much time, it will
> unseat itself from the low indentation at the bridge edge
reestablishing
> the gap and giving the illusion of it riding up the pin.  Tapping down
> may work for a short time, but it also probably exacerbates the
problem
> by further indenting the edge of the bridge.  Either way, the string
is
> not climbing the bridge pin and the better solution is to use some
kind
> of bridge top material or preparation that makes it less prone to
> indentation.  Delignit material seems to be the hardest in use that I
> know of, but does require a power notcher.
> 
>     
> David Love


That's the basic scenario. Additionally, even with a notch cut too 
deep, or the edge crushed below the string, the false beats and tone 
fuzziness that prompt techs to seat strings don't happen if the pin 
is made solid in the cap. The pin being loose is what makes the 
problem noises happen. The cap damage makes it possible for the 
loose pin to do it's thing.
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