Simplified Rosette Jig

Details

Published on Friday, 10 February 2012 17:19

Written by Bo Walker

I stole this idea from Steve Kinnaird and decided that I was just the guy to figure out a way to get out of any extra work by cutting corners on my version of it. In all honesty though, I was mesmerized with the version Steve showed us at the December meeting and I just had to have one. If you have seen the beautiful precision of Steve's guitars, you'll know why I was so motivated to emulate this gizmo!

Most of you reading this are fairly savvy about tools, jigs and general shoptalk. Writing is not my specialty so I hope my rambling style doesn’t confuse anyone. I will try to be concise. Note: As you read this article click on any small image to view a larger image in a separate window.

Materials list:

The jig shown here is simple to make and it does a really neat job of making custom rosettes. It is adjustable for narrow or wider rings by simply drilling two sets of clamp locator holes at different diameters around the disk. The disk may also be changed out to make for smaller sound holes. Identify your design and modify this procedure as required for your needs.

1. Drill a 1/4" dia hole in the plywood disk (d) and turn, rout or sand to match the desired inside diameter of the finished rosette.

2. Using a compass, draw a circle on the base (a) to match the desired outside diameter of the finished rosette PLUS 1/8". The extra 1/8" allows room for the cam clamps (b) and rods (c) to operate properly.

3. Using a protractor, subdivide the circle by 16 (22.5 degrees) and drill 16 1/8" dia. holes 1/4" deep around the circumference of the circle. In the view above you can clearly see a second row of drilled holes at a larger outside circle. This row will accommodate making a larger rosette by moving the cam clamps outward.

4. Drill a 1/4" dia. hole 1/4" deep in the center of the base where the compass point pierced the surface.

5. Cut 16 PCs 1/8" brass rod (c) in 1/2" lengths.

6. Make 16 cam clamp levers (b) as shown at right. Drill the 1/8" dia. holes slightly off center to form the eccentric cam. Some experimentation may be attempted, but I rushed mine and it works just fine. (Image is 100% of the actual cam size)

7. Apply a paste wax to the top surface of the base, remove any excess and buff. Glue in the 1/4" dowel and tap in to the bottom of the hole. As a safeguard, I also used a wax paper disk which was cut to a diameter about 1/16” larger than the OD of the finished rosette. I cut a hole in the center of the wax paper disk and mounted it like a phonograph record on the dowel. Carefully wrap the plywood disk edge with one layer of 1/2" masking tape so that the excess tape can be folded over on the top and bottom surfaces. This will prevent an accidental superglue disaster from occurring during the buildup of the rosette. Now mount the plywood disk on the dowel.

8. Install the cam clamps and pins taking care to tap the pins in to the bottom of the holes. At this point your jig should look similar to this view.

9. Using a sharp box knife, cut the veneer strips using a straight edge. Veneers can vary in thickness so be careful to use the same thickness' for a uniform appearance. Select veneers for color and texture. I used maple and mahogany simply for the contrast.

10. Wax the plastic caul (e) remove any excess and buff. Now place the caul inside the clamping area and set all clamps to the "loose" position.

11. Arrange the veneer strips in the desired order around the disk and inside of the plastic caul. (Below left) When installing the veneers, trim them to fit with sharp wire cutters (below center)

12. When all veneer is installed, and with the caul between the clamps and the veneers, you are ready to tighten the clamps evenly around the jig. Take your time and adjust all clamps to ensure a consistently smooth diameter with no gaps around the entire rosette. (Below right)

13. The "dry" assembly is now ready to flood with CA glue (I prefer the thick CA ). As you work around the jig coating the rosette, be careful to work glue into all seams and avoid the disk or plastic caul.(Below left) When the glue application is complete, spray the entire rosette with accelerator and wait one minute for the "kick" to set up. (Below right).

14. Once the glue is set, release all clamps and rotate the plywood disk and rosette until it comes free as one unit. Carefully turn the disk over, locate in the dowel and repeat the glue/spray routine on the underside of the rosette. Leave the clamps loose because they are not needed at this point.
Sand it flat to 1/16" thick for installation in the soundboard. If you want a larger rosette, omit the sanding operation and go to the next steps.

Want to make a larger rosette?

With a little more work, you can make a larger rosette by adding some “wood tiles” (left) and a few more veneer strips (right).

This allows for the second disk (made earlier) to be mounted concentrically with a dowel when glued together as shown (right). Cut the disk in two parts about 1/2” away from the center hole. This will make one part slightly larger than the other. (The larger part will still have the hole in it) Install the dowel and glue this part to the base with Titebond.

Re-saw the tiles into 1/16” slabs as shown (right) and then you will be ready to trim them to a precisely fit inner ring of the rosette.

The trimming jig is very simple to make by just looking at the view. Using the remaining part of the cut disk, cut the pie shaped wedge so that either angle from the diameter will mate snugly to its adjacent tile in your assembly. You can make any adjustments to suit your particular needs. Short tiles with long tiles, a series of small tiles, etc.

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