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Has anyone here modified the blade of a circle cutter to cut the trough for a rosette? I know it can be done as I've heard it talked about and I've seen one. Problem is, the one I used was about 6 years ago and I cannot remember exactly how it was ground. Any info and picture would be much appreciated. Thanks.

This is the circle cutter I am refering to

Just sharpen it really well.

Replace the center bit with a 1/4" straight rod, and pre-drill the soundboard. Set the blade so the flat edge is "out" for each cut.

Turn the cutter by hand! Do not use the drill press for any other purpose that just holding the whole thing in alignment. It will only take a few turns. Make sure that the table is square to the cutter.

Turn the blade for the other edge.

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It's passed me by. How does that cutter create a flat bottomed channel?
Does Cumpiano feature one in his book?
I use one but I dispensed with the cross piece and cutter. Unfortunately my version did not have the separate cutter (as shown in your photo). The cross piece and cutter was one piece - a little like an Allen key. That was fine for the outer cut, useless for the internal one.
I fabricated the replacement from Ebony, using a wedge and thin scalpel blade for the cutter. It only marks the outer and inner circumference. The actual channel is cut with the small router plane.
The circle cutter is set (inner/outer circumference) using the internal jaws of a digital caliper. With the caliper you can accurately dial in the width of your actual rosette, plus a bit more to allow for any expansion when the glue hits it.

http://www.luthiertool.com/accessories.html

This guy sells high speed steel cutters that are flat. I've purchased a bunch and ground them to different thicknesses for installation of purfling, herringbone, and abalone strips, which I chuck into the circle cutter you have pictured, per William Cumpiano.

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