[pianotech] Renotching-Repinning-Reusing Bridges in rebuild

William Monroe bill at a440piano.net
Wed Jan 20 15:14:46 MST 2010


Hi Joe,

My procedure doesn't differ all that much from yours, but here goes:

1.  Pull old pins and record size - discard into recycle bucket.

2.  Resurface bridge, either using a handplane, or sandpaper, depending upon
the amount of material to be removed, whether or not the bridge cap has any
steps in it, and my mood.  I don't specifically remove the old DAG first on
an old bridge - it'll just get DAG again in my shop so.......

3.  Sand the sides of the bridge.

4.  Vacuum up the mess, then blow the old bridge pin holes with compressed
air.

5.  Apply DAG - judiciously.  I try not to slop over the edges, into the
notches and such, but I'm not obsessive.

6.  Re-Notch bridge to the pin hole centerline or just behind it (into the
bridge, that is) - Makes the bridge pin the termination point for the
speaking length again, and cleans up the notches.

7.  Epoxy in new bridge pins with West System, then, while still wet, use
panty hose (I prefer knee-highs  [?]) in a shoe shine method to remove excess
epoxy and seal the notches, and the bridge root.  I've tried two different
ways to apply the West System: the first method is to mix it up, put it in a
hypo-oiler and (using a spring clamp to speed up the flow) fill the old
bridge pin holes with the stuff.  I find I need to mix in two batches this
way, sometimes three.  The other method is to mix a small pot of West
System, and dip the pin prior to driving it.  I think I prefer the latter
method.  It's a bit quicker, and I only have to mix one batch, but the first
method will do a better job of filling any voids or cracks in the bridge
root.

8.  Level Bridge pins with a belt sander and high-quality belts - it makes a
huge difference.  I used to use coarse grit belt, followed by a quick filing
to clean up, but now I level them with the coarse and clean them up with a
p220 belt.  Coarse grit does a good job of not heating the pins up, so long
as you don't sit in one spot from start to finish.

9.  With the board taped off, shoot the whole mess with lacquer.  Unless you
use a coatings epoxy, it is not UV resistant, so lacquer on top.

Of course, as with any of my "systems," I'm not married to the procedure and
there is room for exceptions/changes, depending upon the condition of the
bridge cap, depth of grooves, downbearing/crown measurements, etc.

William R. Monroe





On Tue, Jan 19, 2010 at 11:04 PM, Joe DeFazio <defaziomusic at verizon.net>wrote:

> Hi all,
>
> I would like to get some feedback from the rebuilders on the list about the
> procedures that you follow in reusing a bridge without recapping.  I am
> always tinkering with my methods (in an attempt to improve them,
> hopefully!).
>



> SNIP
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