Are you looking to make a solid wood rosette for your guitar project that's different than the norm? That's what I wanted, so I decided to design one and cut it out the parts with a laser cutter and CNC router. If you have access to those tools, this is a very easy and fun way to do it!
3mm solid wood piece (as big as your rosette needs to be)
Step 1: Laying Out the Center-points for the 3 Circles
I used Fusion 360 for this project. First open a new page and select your starting plane. Then draw 3 points roughly equidistant apart. This will be the starting points of the three circles, which will make the rings of the rosette.
Step 2: Draw the Circles to Form the Rings
Now draw three different circles of the same size, starting with any of the points. I made these 180mm each (outer diameter). Then draw an inner circle diameter for each circle, which will form the ring. If you'd like a 5mm thick ring, then draw the inner diameter circle at 175mm. Repeat this until all three rings are formed, for a total of 6 circles, as seen in the example.
Step 3: Refine the Sketch to Prepare for Laser Cutting
In order for the laser cutter to cut the 3 rings out as a single solid piece of wood, you will need to remove parts of the sketch. At each intersection, you'll see cross-over pieces that need to be trimmed out (note red piece highlighted). Remove all of those cross pieces and then export the sketch as a DXF for the laser cutter software.
Step 4: Cut the File With the Laser Cutter
Bring the file into the laser software to prepare it for cutting. Set the power and speed settings as needed for the type and thickness of wood you are cutting. It's ok to make it thicker than the depth you are going to cut the receiving channel for the rosette in the guitar top; you can sand the extra off later, once it's glued in. Load the wood into the laser and once the focus is set, cut the file.
Step 5: Create the Model for the Guitar Top Surface
We will now use our design to create a CNC file that can be used to cut the channel in the guitar top to receive the rosette. First create an offset construction plane below the rosette design and then extrude it up to simulate the guitar top wood.
Step 6: Cut/extrude the 3-ring Rosette Into the Top Design
Next, extrude our 3-ring design to be a solid 3D object. The last part is to extrude the 3-ring object down into the guitar top as a cut procedure; this will leave a channel which we can then mill on the CNC. The depth in which you cut the receiving channel down into the guitar top should be less than the thickness of your 3-ring rosette piece. You can also make another circle in the center to cut out the sound hole at this point, as well.
Step 7: Create Tool Path for the CNC to Cut the Rosette Channel
If your rosette is 5mm wide, you'll need a 5mm bit or smaller. Set the depth appropriate to your wood thickness and do test runs. When the test runs are complete and you are ready for the final cut on the real guitar top, double check the position and settings of the cut. You want to put it exactly in the right spot for your guitar top layout and design. I found with my type of wood used that I needed to create an addition tool path that milled out some small leftover pieces; some wood types can easily be tended to with a small chisel. Also, you may need to create an offset adjustment in case your rosette is too tight. Tight is OK, as thin super glue can be used to glue in the rosette, once it's in place. There is almost always a final fit of perfection adjustment needed in this stage, which can vary with the types of wood that are being used. With patience and test pieces, a perfect fit is very possible.
Step 8: Install the Rosette!
Depending on how you placed your initial starting points for the circles in your design, the rosette may or may not be fully symmetrical. In any event, it's best to lay the rosette on top of the channel in a few different ways to see where it actually fits natively. Once you have it lined up, carefully insert it evenly and wick in some super glue and voila´ -you have your very own rosette, designed from scratch! Congratulations, now all that is left is the rest of the guitar!