Installing a Rosette
So, why install a rosette in the first place? It's a lot of extra work. Well, the rosette really strengthens the area around the soundhole. Without it, the soundhole edges can be damaged easily and the cracks may run into the face of the instrument. The rosette is also a real focal point of the uke's design, and is a nice touch! On this instrument I am doing a simple abalone rosette.
There are many ways to install a rosette, both hand and power methods are in common use by luthiers. I use a router to perform this operation. If you want to do it without power, you can find Exacto circle cutters in hobby stores. I have also seen people use a stick, like a popsicle stick, and simply use a brad for the center pin and an Exacto blade poked through the stick for the cutter. Primative, but workable! If you do the hand method, you will have to cut the inside and outside edges of the rosette and chisel out the middle. I did this many times in my early luthiery days and it works fine. Just go slowly during the cutting, making many passes, so that the blade cuts straight.
An alternative power method is to use a circle cutter on the drill press. Here are a couple of circle cutters. The first one shows a cutting blade that I took off of my purfling cutter. The second one shows the standard cutter that you shape on a grinder to fit your needs.
Before starting the rosette, sand the top smooth on both sides to about 3-3.5mm. Sanding to 80 grit is smooth enough at this point. Find the center of your soundhole and lay out both the soundhole and the inner and outer edges of your rosette decoration. Put a coat of whatever kind of finish you plan to use on the bare wood. If you plan to use oil, you might skip the finish as it may interfere with gluing. If you are working with wood, that is thicker than the top, it will be inset and sanded off after it is glued in. If you are working with shell, you want to cut the depth of the channel so that the shell is just slightly below the level of the surface. If you leave the shell standing above the top surface, you take a chance of either sanding through the shell or into voids in the shell. In any case, make sure you do not cut the rosette channel all the way through the top. Once the rosette has been installed you will sand the face only enough to clean up the inlay and then do the rest of the sanding from the back side.
Rosettes can be a premade decoration that you install all at one time, or several pieces that are all loose until you do the work. In this series of photos I am installing a simple abalone rosette with a black veneer border. Thin veneer purflings are available from luthiery supplies, or you can cut strips from sheets of veneer. Whether installing a wood, plastic, or shell decoration the process is very similar. With wood you would normally use Titebond glue. For plastic use the appropriate plastic glue. For shell you can use either superglue or epoxy, though I have also used Titebond sucessfully. If you are installing a rosette in a spruce top, do not use superglue. The glue can seep into the endgrain of the top and might show under the finish. Titebond and epoxy are acceptable glues for spruce, redwood, or other softwood tops.
I use a 1 H.P. Sears router for cutting my rosette channels. Dremels work, but do not cut very clean unless you go very slow. On the router shown I use a standard Sears circle cutting jig that I modified to accept a 1/4" pin (shown in the second photo below), which fits into a bearing on my workboard. It is difficult to produce good results using the normal trammel point that comes on a circle cutter.
My workboard might be of interest to anyone with a cement floor. I drilled and chipped out a 4" hole in the floor. Into that I cemented a 31/2" galvanized female coupling. My various workboards sit atop a 4" x 4" post fitted into a 3 1/2" piece of male threaded pipe at it's base. This allows me to have an easily removable work station that I can walk around and at a height that I can see what I'm doing when routing. I used materials that I had around to make this work station. A solid pipe would be better than the pipe/4 x 4. The workboard has a small bearing with a 1/4" center inset to receive the pin on the router base.
I always clamp the top to limit movement during routing. I did not used to, but I get a little better results when I do.
Here is a good reason to wear safety glasses. This is the cutting end of a 1/8" router bit that broke off. I use 1/4" shaft high speed steel bits with either a 3/32" or 1/8" cut. I set the router to make the first cut at the inner edge of the rosette and then adjust it, moving outwards, until my rosette decoration fits. It usually takes me 3 adjustments to get the fit I want.
Here you see the 2 black veneer border strips and the abalone strips I will inlay.
I work with real shell, but the process is the same with Ablam. I start with curved strips and break them into pieces about 1/4"-3/8" long to make the circle. You do not need to sanded the breaks flat.
Here is the finished rosette. If your fretboard extends to the soundhole, there is no need to inlay under it. I fill that space with epoxy.
In the next session I will move on to bracing the top. Any questions, just e-mail me at pegasus@hilo.net