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This tool is great for marking and cutting the rosette trough, the soundhole, and the soundhole reinforcement material. It is well suited as a marking/cutting tool whenever a radius is called for. The SPCC is milled from aluminum and the radius is adjustable from 1 3/16" to 4" radii, with a fine thread mechanism. A ¼" drill rod is used as the registration pin. The blade is high carbon steel made by Ron Hock and is held in place with an Allen head cap screw. The blade block is locked in place by an Allen bolt. Wrenches for each are included.
Beginning with a compass, mark your rosette or soundhole lines. Set the depth of the knife. Mount the cutter on the 1/4" pin that protrudes from your backing board and soundhole centerpoint and begin cutting. Your soundboard should be thickness sanded before attempting to cut out the soundhole as the blade cutting depth is limited.
NOTE: Make sure that the flat side of the blade faces the ledge that is to be 90 degrees. On the initial pass, rotate the cutter slowly as you move into the grain to avoid tearout. Be sure to keep your blade sharp.
Luthier and instructor Robert O'Brien shows how to use the Rosette Circle Cutter in 3 parts: