Cutting the Rosette Tiles

Here's how I do it.   I have a "precision" router set up.   You can see it in the photo, and I will admit right up from there are a few design flaws in it.  First, as you can see, the router base itself is attached to a plexiglass base.  This actually works rather well for the operation I am about to describe, in part because the base itself is wide enough that it covers the round of tiles.  There are three slots cut in the plexiglass, two for the adjustment mechanism, one for the pivot pin.

The adjustment mechanism is basically two steel rods that pass through the hold down and the pivot.  The two rods are epoxied into the pivot.  The two carriage bolts pass through the plexiglass and serve three purposes: (1) sliding in the slots, they serve as a gross adjustment, (2) they lock the steel rods in place, and (3) they lock the adjustment mechanism in place.  It isn't perhaps as visible in the photo, but but there is a saw kerf cut through the holes for the rods.  The carriage bolts pinch the rods when the wing nuts are tightened.  That is the first design flaw.  I should be able to loosen the rods without loosening the adjustment mechanism, but I have discovered that the "precision" mechanism can be adjusted by loosening the two carriage bolts just slightly, holding it in place with my thumb as I make the adjustments to the screw, which serves as the precision mechanism.   

The "precision" mechanism is simply a 1/4 by 20 steel rod that passes through a bolt inset into the adjustment mechanism into the pivot, where I inset a washer and a bolt.  To make the radius smaller, the "precision" mechanism is adjusted clockwise, pushing it out or closer to the router.  To make the radius larger, the "precision" mechanism is adjusted counter-clockwise, pulling it in or further from the router itself.  It works reasonably well, but there is some play in it, and that constitutes the second design flaw.  Someday, I may break down and buy the set up sold by Stew Mac.

The first step in making the rosette tiles is the template jig, the second is cutting the slices that will be used for the inlay, and the third is shaping the pieces to fit the jig.   My sound hole is 1 and 7/8 inches in radius, so I scribe a circle of that radius on a scrap of 3/4 MDF.  I also scribe a line at 2 and 1/8th for the inside diameter (ID) of the rosette, and then 2 and 5/8th for the outside diameter.   I scribe two copies of the rosette.

The next step is to use the rosette template to cut a couple of circles that will produce a template that is the mirror image of the rosette channel.   You can see it in the photo above.  I set my router to cut an OD channel, then an ID channel, leaving the mirror image of the rosette channel proud in the center.  This will be used to shape the inlay pieces.

The inlay material itself is a pile of wafers cut from the end grain of the padauk at about 1/8 thickness.   Normally, I would use my band saw for this, but I'm still awaiting parts, so I use a cross cut sled and a stop, and grit my teeth at the waste.  I put double stick tape on the proud rosette channel, then tape the wafers to that.  Make certain that they are secure.  If they wobble around you will not get precise cuts.  You can see that pictured above.   

I then cut the ID and OD with the router set up.  It pivots on the pin pictured.  It will take several passes, so again make sure the wafers are well secured with the double stick tape, and that the router base does not catch on an edge.   Cut the OD and then the ID with the router.  For the second batch, I leave the router setting in place for the ID, and cut the ID then make the adjustments to cut the OD.  For the third batch, I leave the router setting in place for the OD then make the adjustments to cut the ID, alternating until there are enough shaped tiles. 

The next step is to cut a channel that will fit the rosette tiles.   I consider this practice before I cut the channel in the soundboard, but it also serves a purpose as a jig to get the angles correct on the ends of the pieces.  I will cut a kerf through the rosette channel on the table saw, then use the kerf as a guide for trimming the ends with my gents saw, using the kerf as a miter box.  By the by, to get the pieces perfectly sized, I cut the rosette channel to fit the narrowest piece as precisely as possible, then make adjustments to the other pieces with sandpaper.  Be cautious not to round over the ends if you have already cut the miters, or sand to fit before you cut the miters.  Also, it always a good idea to have several more tiles than you need.  Because they are cut from end grain, they are fragile, and if you break one (and I broke two) you don't need to go through the whole business of the router set up again.