Official Luthiers Forum!

One of the coolest, simplest circle cutting rigs I've seen is just an oversized plexiglass base on a lam trimmer, with small holes drilled through it at various distances from the center. Say you're cutting a rosette: you drill a hole through your top in the center of where your rosette will be, and through a workboard beneath. Stick a pin through the top and down into the workboard. Choose the appropriate radius hole in the lam trimmer base and put it over the pin. Fire up the trimmer and lower it down into the wood. With a little care, it's not hard to lower it down accurately, so a plunge base is not needed. Twirl it around on the pin, lift it back out. Voila. After doing it this way, I see no need for any fancier jig or router base for cutting rosettes or soundholes.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Todd,

Are those plexi bases for lam trimmers available commercially with the holes predrilled for different radii? Or, does one just have to measure from the center, and drill the small holes for whatever radius you want?

CrowDuck

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Chris Nielsen
Soquel, CA.

Chris,they're available commercially, but very cheap and easy to make yourself.

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Scott Thompson
Port Townsend,WA

"In a perfect world we'd all sing in tune
But this is reality so give me some room"
-Billy Bragg

It's a make-your-own deal.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Sylvan, very cool. How small of a circle can you cut with that?

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Scott Thompson
Port Townsend,WA

"In a perfect world we'd all sing in tune
But this is reality so give me some room"
-Billy Bragg

Oh, Scott says they're available commercially. I didn't know that.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Scott -
The limit on my circle cutter is right at a 3 1/2" diameter.Sylvan38768.9481597222

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Sylvan
http://www.wellsguitars.com

   I'd be very careful about using a fly cutter or any large diameter swing type cutter for your rosettes. The problem lies in the nature cutting edge on the tool itself rather than the principle behind the cut.

   The tendency of most that are avaialable and offered by lutherie tool vendors is to tear or separate the grain of the top at certain points in the circle cut for the rosette.

   Holding a top wit the grain running vertically in front of you after using most fly style cutters, you will notice, many times, pulling of the grain in the 4 to 5 o'clock and 10 to 11 o'clock positions on the rosette edges. It's just the orientation of the grain at those points and the way the cutter is forced to pull against it while working. Those small tears become more eveident with the application of glue used to install the rosette.

   Whether the tooling is sharpened to a positve or negative rake angle, it can still be a problem.

Just a thought,
Kevin Gallagher/Omega Guitars