Building the Rosette

I've been working on building the rosette that goes around the sound hole on the guitar.  This turned out to be a rather challenging thing to build.  The inner and outer rings are multiple layers of veneer alternating light (maple) and dark (gum wood).  I found the gum wood at Hardwood Heaven, a local supplier of hardwoods.  Unfortunately they didn't have much of a selection.  They had one flitch of a burly maple, which I bought, but decided that it looked too nice to use someplace where you wouldn't be able to see the figuring in it, so I'm saving that for something else.  I ended up using a package of 3/4" wide edge banding with a heat-activated glue.  This actually worked out pretty well.  

The form is a 4" diameter circle cut out of a 2x6 using a hole saw.  Since the outside diameter of this block is actually smaller than the sound hole will be (it's the inside diameter of the hole saw and the sound hole will be the outside diameter), I first glued a few layers of cardboard around it to build it up.

After gluing the inner rings, I tightened a couple of hose clamps around it and let it dry.  The center rings are made up of small pieces of wood.  I would have liked to have been able to cut these a lot more accurately than I did.  They're not as uniform as I would have liked. It also didn't occur to me at first that the ones on the outer ring would need to be a tiny bit wider to account for the fact that the circumference is longer.  The circumference of the outside of the ring is longer by 2 × thickness × π. If the pieces are 1/8" thick, that works out to more than 3/4".  Divide that by the number of pieces (45) and you end up having to make them just barely wider.  If you don't, the pattern will eventually not match up.  The angles have to be different too.  It's a 30° angle on one side and 35° on the other.  They had to be glued on a few at a time or else they kept shifting. Once the inside row was glued, I clamped it and stuck the whole thing in a 300° oven for five minutes.  This allowed the glue to soften and the clamps could be tightened some more.

Next I added the big carriage bolt you see in the picture and chucked the whole thing in a drill.  With the drill on a low speed setting, I held a rasp to it to smooth out the rough edges. Then I added another light strip (hard to see in the photo) and repeated the whole process for the outer rings.