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Hesh,
How do you mark the footprint of the bridge on the top of the guitar so that it is .005" smaller than the bridge? Do you make a template or is there some cool trick. I've been wanting to try this for awhile but couldn't figure out a good way to mark the top. Currently, I use the bridge as the template and score around it with a sewing needle. That has all of the problems you mentioned above.

Hi Mike: Typo on my part and it should read .050".

Simply tracing the exact bridge pulled back a tad (approx .050") from the IGS (It's gonna show) line using an X-acto or single edged razor blade being careful to only score finish and not top fibers get's it done.

Those decimals will get me every time....

I locate the bridge and hold it with two 1/16" brads in the saddle slot. Put low tack masking tape under the bridge, score the tape along the edge of the bridge and remove the bridge and tape from the footprint. That gives an exact footprint. Then I score a little inside that line freehand all the way around, finish only, and rout to that line and clean up with little sandpaper blocks and scraping. I usually do not rout all the way to wood. Sometimes it is not so easy to be sure you have cleaned off all the sealer. I look at it from different angles of light.

For the bridge ledge I do trial routs on scrap until I get a depth that just clears the finish and is wide enough. Usually 2-3/32'. Then rout the ledge on the bridge.

Most difficult area for me is the 90 degree corners at the ends of the wings, you really have to be careful to get then clean or the wings may not seat properly.

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.

Yep the corners can be tricky AND risky too since chisels can slip. A super sharp chisel helps here a great deal and the scoring of the finish is important too to prevent going too far.

One of the advantages of chisels over routing the finish off is that with a chisel you can get tight corners with a router bit they are rounded and will have to be cleaned up with a chisel for the bridge rabbit to seat properly.

I don't know Tony. I rout out the finish within my bridge outline .093" and have never had a bridge come up in 30 years of building. Part of the problem with routing off a finish is that finishes want to chip, no matter how new your bit is, so leaving yourself a little extra room is prudent. Consequently, I inset the joint. As Hesh and David have remarked, what's most important is that the glue joint is clean and tight. Most of the bridges that I've seen come up from the factories have had a squiggle of glue underneath them and have not even bothered to brush the glue the length and width of the bridge. The other important thing is to allow more than 24 hours to pass before putting string tension on it. I've also seen people use too much water trying to get excess glue up and this too could be a problem in that water can weaken the glue at the very perimeter of the bridge.

Anyone routing the finish off with a guitar will find that there are variations between their template and the guitar top and it's inevitable. Scribing around a bridge will also cause fibers to be cut because you're trying to get through the finish.

I contend that routing into the wood a little bit is probably OK. That is because the bridge is still glued to full length fibers. When you score through the finish, however, the wood becomes very weak.