Welcome Guitarists, Luthiers and any one else who is interested. This is a straight forward method for producing accurate rosettes. A nice rosette gives the guitar great character and can harmonize subtly with the other design elements of the instrument or otherwise they can be an eye catching focal point for the guitar. This stepped design, although small and simple, works nicely in the finished rosette.
In this design there are seven files with six veneers in each. The first, from bottom to top is white, red, white,white,white,white. Each file will become a separate glued up sandwich of .5mm veneers, this sandwich is cut into planks and thicknessed. Eventually the seven different planks are glued together forming a log, the "end grain" of this log produces the mosaic.
the veneers must be checked for uniform thickness, if they are not uniform they can go through a scraping jig.
The veneers are cut to the length of the clamping jig about 240mm, they are all cut the same width. The wider you cut them the more of that design you will have.
This glue is quickly spread with a card.
This is particle board cut from a kitchen bench top, the veneer stack won't stick to the laminex surface.
The stack of veneers are clamped over night.
The marking gauge is set to less than 1mm, if cutting by hand use a Japanese Ryoba saw.
The band saw is quick. After cutting a plank off the stack, the stack needs to be jointed with a block plane before cutting another.
Now the planks need to be thicknessed
A super sharp, finely set small plane is used. Veneer shims can be glued on the sole to keep the plane square and to reach a final thickness of .5mm. The photo below shows a simple scraping jig being used for a more accurate final thinning of the planks.
The planks are arranged into correct order and brushed with slightly watered down glue.
A small straight edge the thickness of the log is clamped over the top of the planks lightly at first, then the planks are clamped or wedged. No great pressure is needed.
The mating edge of the log is slightly tapered down its entire length with the plane, this gives the profile of the mosaic tile a slight wedge shape. The log is then cut in half and glued together. Pvc pipe with sand paper glued to it is used to put a minimal curve into the underside of the log. The top of the log also needs a slight curve (convex) across its width, this helps the mosaic tile fit the radius of the rosette. A small design like this needs very little radiusing and tapering.
The tiles are cut with a fine back saw or dozuki saw to about 2.5mm or more.
The next stage is to balance the mosaic design with strips of veneer and herringbone
The strip of herringbone is thicknessed in the scraping jig, this helps keep the strip and the rosette uniform.
The photo above shows a rosette built around a disc. Glue is spread onto a veneer band, pinned or wedged in place at the top and then wrapped tightly around. This grabs quickly and the next band can be added straight away, the herringbone strip needs to be pinned.
This is the jig my uncle used years ago when he made rosettes for me.
The rosette is assembled dry in the waxed jig. Here i choose to use super glue, but care must be taken, or the rosette may be glued with Hide glue or Titebond as it's assembled in small stages.
In the photo above you can see the last outer white veneer (sacrificial), which is waxed. This can be made just the right thickness so the rosette is snug in the jig.
The rosette has been thickness sanded, you can also just plane and scrape in the jig until the rosette is about 2 mm thick.The rosette is about 19.5 mm wide.
The inner radius is taken from the inner disc of the jig and the rosette is aligned over this cut. Then The top is marked here and there against the outer edge of the rosette with a sharp pencil. The sharpened blade of the circle cutter is brought to the edge of these marks, locked in place and lightly and slowly cut into the top.
This channel has been cut with a router as well, its depth is almost the thickness of the rosette.
The rosette is clamped and left overnight.
It can only be scraped when its dry.