Category Archives: Thicknessing and Rosette

Thicknessing the top plate and installing the rosette

Thicknessing top plate and installing sound board rosette

After I take the plate out of the clamp I clean up the glue with a sharpened scraper. I then take it over to my drum sander and take it down to 3.0mm. I had a little offset on the glue joint so I had to even it up on both sides before taking it to final thickness. The final thickness on the drum sander is 3.00mm.

Out of the drum sander I used a 30cm length of jointed sanding block and hand sanded the plate with 180 and then 240 grit. Once again the spruce is soft so even this kind of sanding will add in reducing the thickness. At this point if I hold the plate between two fingers and tap it with my knuckle I can hear a resonance. I check often using this method.

Next step is to trace my shape onto the plate. I use my full plate template for this carefully lining up the center line.

I am now ready to mark my center position for the sound hole. The center point of my sound hole will be 148mm from the top of the body outline. And the sound hole will be 100mm in diameter. At this center point I drill a 8mm hole, which is the diameter of the axis I user on my Dremel router trammel.

I am now ready to route a 1.35mm trench in the top plate for the rosette.

Clamp plate down onto your work board and insert the trammel axis. (There is a 8mm hole also drilled into the work board)

Set your distance from the center and begin by taking light passes. Final depth will be 1.35mm.

The first trench done. There will be three in total.

Repeat procedure for each of the three rosettes we will install today.

After checking the fit of each apply glue and install the rosettes. Apply some clamp pressure (I used a long reach clamp and caul to get right on top of it) and let sit for a few hours before taking out of the clamps. Here we see all three rosettes installed.

Route out the center sound hole at 100mm diameter. Make sure you hold down both pieces as you get close to the final pass or you may find the center hole will rip away damaging your plate.

Cool, it’s taking shape.

Finally take it over to the band saw and cut away about 6mm away from your line.

For the last step in this rosette installation I use a well sharpened scraper and bring the rosette, which should be a little proud, flush to the spruce sound board. Then sand lightly (I am careful to not impregnate the spruce with any black dust from the rosette) with my sanding block.

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