Radius Cutter

I found a little time to mess around in my shop this morning, and I came up with this radius cutter that I will use to cut my rosettes.  I was able to get into the school shop, and we have a great band saw with a re-sawing blade.  It cut the redwood like butter.  I will begin work on the soundboard, beginning with the rosette.  I have something in mind, but don't know how well it will work.  I'll give it a whirl and let you know if it does. 

The construction of the radius cutter is fairly simple.  I had some 1/4 inch oak scrap left over from the bench, so I cut a 1/4 in dado in the sides of the cuter, and at the same time, cut for the end pieces and the slide, but did them on both sides.  The pieces are laid out on my bench.
 

The slide works fairly well.  I took a section of what I'd cut for the end pieces, enlarged the dado slightly.  I drilled a 5/16th hole for the blade, and squared it off with my 1/4 inch chisel.  I drilled a 1/4 inch hole for the carriage bolt, then cut it in half with my gent's saw, pushing the blade up against one side of the dado.  The slide is held in place by the carriage bolt, which pinches the two pieces against the interior slats, and the blade is held in place with a small shaped piece of the slat.  It all pivots on a 1/4 metal pin that goes in the hole on the right. 

The blade is made from an old jig saw blade.  I did some very preliminary work on the grinder, but it will need some additional shaping.  I have in mind a chisel point so I can turn it in both directions, and will work on some when I get up in the a.m.  I should be able to do that without waking my wife and our guests.  Even with the point only partially sharpened, however, it did cut a good groove in a scrap of birch ply, at about 1/32 of an inch wide.