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There are several factories that use routers to remove the finsh beneath the bridge. I use a Dremel with a 1/8" bit so it's a bit slower but easy to control.

Martin leaves 3/32" of finish under their bridges and that is where I picked it from.

The reason I don't use hide glue as there is a void around the perimeter where the bridge is sitting over the finish and hide glue will not adhere in voids and actually crystalizes in voids. It will hold in the center where the bridge is clamped in place. LMI's white glue will hold and fill in small voids.

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tim...
http://www.mcknightguitars.com

So what is the advantage of doing it this way?

Yes, Mario, don't leave us hanging!

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http://www.presnallguitars.com

I route. No biggie there. But I also clean it all up right to the scribed line, not leaving my bridge sitting in the air.

Tim, I can't believe you're doing this. Those factories(yes, factories: aren't hand builders supposed to do better, and not cut these corners? Repairmen have a steady stream of Martin's with lifted bridges coming through....) that leave the small ledge also cut that ledge into the bridge, so that the part that is glued makes full contact! You're leaving your glue to fill a, what, .005-.010" gap? Huge! The only glue that is a reasonable gap filler is epoxy. All other work chemically by joining wood to wood. Let's not even talk of the gasket effect....

If your bridge is large enough, the 1/32" you leave off isn't all that bad(although it is a substantial percentage of your glue's surface area, maybe 10%, and on my bridges, would be near 20%), but cut a ledge on the bottom of your bridge so that it makes contact with the top, for God's sake. Better yet, use all of the bridge's surface for glue.

This should be filed under: obvious.

Hanging head low, feeling scolded ... A G A I N ...


I will do an A and B test and offer feedback on the "gasket effect". My finish at the bridge measures .003" - .004" thick.

I too had doubts when I first investigated this bridge attachment technique. I spoke with three other well known small production builders who are using the same method with no ill effects. One luthier mentioned that the circumference of finish left under the bridge actually compresses and they get a very good mechanical contact between the top and bridge bottom. Another luthier uses CNC [extensively] and mills a ledge around the perimeter of the bridge to allow the bridge to set directly on the top.

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tim...
http://www.mcknightguitars.com

Okay, I just finished gluing down the 7 bridges...I decided to take different avenues to see what I liked best (or hated least!)...different combinations of routing, scraping, stripper, vacuum clamping and LMI-type bridge clamp. Routing is scary for me...stripper not so much, but I'm worried about the gluing surface after having the stripper there...I did wipe the area down with wet paper towels before removing the tape mask, and then scraped with a burnished razor blade, just to convince myself the stripper wouldn't wreck the glue bond (I'm not totally convinced!)...scraping alone was fine til the 3rd guitar or so, then I quit before I got careless. The LMI clamp is foolproof, but on the 12-string bridge I went with vacuum because of it's larger footprint. Seemed to work well, and I'll probably continue to use both methods in the future. I guess scraping is okay and probably safest all around for me, especially for one guitar at a time. Thanks guys for all of the advice...I love this forum!

Larry

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http://www.presnallguitars.com

I picked up a little trick from Brian Burns, which I use for removing finish before gluing down a bridge.

Brian showed me how to make a mini scraper out of an industrial razor blade. You bend it slightly, then run your burnisher over it lightly. The tiny burr is enough for delicaten scraping work, like around the rosette, but it also works great for removing finish where the bridge will go.

I like Lance's idea, though. Think I'll try it next time.

Best,

Michael

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Live to Play, Play to Live

Michael, yep, that's a trick I learned while building furniture...and if I get the hook just right, I get a pretty agressive cut with the razor blade...I try to get one like that, and a slightly less agressive one for close to edges and what not....

Larry

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http://www.presnallguitars.com