Enlarging existing bridge pin holes

[Brad Smith]

Hi David,
Is there any reason that you must use the #10 pin, other than the
'in-between' size of the original?
Nick Gravagne has great articles and an excellent PTG class on
reconditioning an existing bridge; re-notching, etc.
Using West Systems epoxy to fill cracks, and size the existing holes, and
then drilling with one size lower drill bit to enable use of original size
pins.

I just did an M this way, worked very well.  Size #7 pins in the long
bridge; epoxy; drill out with the bit intended for #6 pins.  Install new
#7's.
Buzz them down with carefully with belt sander.    And, I used the hanging
Dremel tool with the flexible shaft thing. (Drill bits from Pianotek).

Of course, you'll have to weigh the decision, since you are not going back
in with the odd size 9 1/2 pins.
If you put enough epoxy into the holes, to then drill with #8 bit, and
install #9 pins...it's likely you would end up with more epoxy remaining in
the drilled out holes.  This stuff is so strong, I would do it with
confidence.  Others may favor the enlarged hole and complete contact with
fresh wood using #10's.

Also, what are the consequences of using big fat #10 pins...or using
slightly smaller #9 pins. Will it affect side bearing, or relationships with
dampers?
Perhaps not enough to worry about.

I'm not sure how critical the type of bit is, obviously it's part of the
puzzle.
Most important is the lightweight shaft that allows you to drill and follow,
without influencing, the angle of the original holes.
For that reason, you would want to avoid completely filling the holes with
epoxy.
And, making a bridge pattern from acetate or Mylar is vital, should anything
go awry.
You might even wish to start a size lower than your final bit, to
re-establish the holes, and then complete the sizing with the final bit.
Maintaining control, and working "intentionally" are most important.

Nick's class also covers a great way to fix bunged up notches; or cracks
that have distorted the notch termination on an otherwise good bridge.
This stuff, done right makes an old bridge look as though you've recapped
it!


Best regards,
Brad Smith, RPT
www.smithpiano.com



-----Original Message-----
From: David Love [mailto:davidlovepianos@comcast.net]
Sent: Thursday, April 28, 2005 11:41 AM
To: 'Pianotech'
Subject: Enlarging existing bridge pin holes


I am repining a bridge and because the bichords are a strange in between
size (about 9 1/2), I need to enlarge the holes to accommodate a #10
pin.  I have not had much luck doing this in the past in a clean way and
am wondering how others approach this.  My thought is to reinforce the
bridge cap with a clear coat of epoxy first before drilling it out,
reaming out any excess that might create large globs inside the hole
before it sets up.  Any thoughts on this?  And what is the best way to
approach redrilling an existing hole: high speed, low speed, by hand?

David Love
davidlovepianos@comcast.net



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