Decapping bridges with a router

[Fenton Murray]

Dave,
I've done this plenty, the photo shows a couple of sleds I use, sorry 
they're not on the router. The router's mounted in a table right now but 
it's pretty simple, the screws go through the base and into the sleds, the 
distance between the 2 is set to manage around the bridge curves. Shimming 
between the base and the feet or sleds is an easy adjustment if needed. As 
Ron says below, watching the bridge elevation is critical, but easy. I 
simply step it down, stoping to make the depth of cut adjustment. These 1mm 
or so little steps are easily taken out with a couple passes of a hand 
plane, sander, scraper or what have you. Another thing to consider with the 
router is the angle you may need on the cap. By using a 1" plunge bit you 
can take small amounts of material in one pass as you sneak up on the final 
dimension with the appropriate (read front) foot shimmed up. You'll only 
achieve an angle on the cap if you take it all in one pass, the one inch bit 
may leave a small edge, but again, very easily trued up later. There's a bit 
of fussing and set up, but I think it's a nice way to machine a cap. 
Actually, I'm describing taking down the new cap to it final dimension, same 
difference though as decapping the old with everything being not quite so 
critical. Of course if the bridge is off the board you can just band saw the 
old cap off keeping it for a reference. With the bridge off the board I have 
also used a slave board to do some of these opps, letting a piece of ply 
stand in for the soundboard and using screws through the ply and into the 
bridge to secure it.
Fenton

----- Original Message ----- 
From: "Ron Nossaman" <rnossaman at cox.net>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Friday, August 01, 2008 8:19 PM
Subject: Re: Decapping bridges with a router


>
>> A couple of years ago I saw (or dreamt) a router adaptation to take the
>> bridge cap off.  It consisted of a couple of elevated skids attached to 
>> the
>> router base that straddled the bridge so that you could basically run a
>> router down the length of the bridge and take the bridge top down--very
>> fast, very smooth.  Does anyone use that system and can send me a picture 
>> of
>> the skids and how they attached them?  I have some ideas myself but
>> shortcuts are always welcome.  David Love
>
> The skid's easy. The hard part is the bridges that go from 40mm at the low 
> end, to 30mm or less at the high.
> Ron N
>
> 
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