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Jameel
Oud Junkie
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Registered: 12-5-2002
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Good points John. I would like to have seen him cut those channels. But you really think it was freehand? The waviness may be from age. Then again a
double-blade purfling cutter, with several light cuts, might ride the ridge nicely. You've obviously put a lot of thought into this, and I really
enjoy reading about your efforts.
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jdowning
Oud Junkie
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Thanks Jameel. What I mean by freehand is to cut the channel to a scribed line by eye rather than by using some kind of straight edge as a guide. The
waveyness observed in the Dias guitar may be due to the cutting tool tending to follow the grain of the wood. Actually, if the degree of crookedness
is small this likely would not be noticeable in a finished instrument.
A readily available tool that caught my attention, as one that might be adapted for the purpose of cutting purfling channels, are jig saw blades - not
the cheap variety that have their teeth set like an ordinary saw - but the high quality ones that have no set. Instead the blades are taper ground to
the back of the blade to provide clearance for the saw dust.
The attached image shows an example of this kind of blade. The teeth are ground at alternating angles - like a chainsaw blade - the sharp points
initially making a scribing cut. This blade tapers from 0.92 mm at the teeth to 0.73 mm at the back of the blade with blade width of 7 mm. (0.036" to
0.029" , 1/4 inch wide). The blade has 10 teeth per inch so cuts very aggressively but I have made a few test cuts to see if there might be
possibilities. I was not able find any finer toothed blades of this type in the local stores so am not sure if they are made. However, the blade could
be easily reground with much finer teeth (using a Dremel tool) - cut straight across like a planemakers float so would have less tendency to wander
off course and follow the wood grain. A short length of the reground blade could then be fixed in a handle and used by pulling the blade for optimum
control (like Japanese saws). The length of blade projecting from the handle would provide a 'line of sight' for guidance along a scribed line (or the
rib glue joints in the case of an oud).
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jdowning
Oud Junkie
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...... and here are a couple of trial cuts made with the saw in a piece of scrap figured maple. Straight grained wood would be easier to cut cleanly
and straight.
If a wider channel than 1 mm is required, two or more blades might be epoxy glued side by side together.
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