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Saturday, May 18, 2013

Arching (part one)

I was thinking about making archtop backs and bellies a while back and I came across an arching pattern from Andrew Mowry's website. This set me to pondering on the best way to do the initial carving on one of these and I decided it called for an overhead pin router. Having previously made the front for a Les Paul guitar, I know how much work is involved and how difficult I found it.

I sketched out my design in Google Sketchup and put it together from bits I had round the workshop (except for the rubber castors which I bought online).

Pin height adjuster
The router height above the table is set using its 'plunge' and the pin height is set with a modified lever-operated clamp mounted underneath the table. The routing table can be adjusted up or down by 10cm if needed as it's fastened with bolts and wing nuts running in vertical slots. .

The real thing...was not quite so neat!
The router is mounted one third of the way across the width of the table to allow wider pieces to be worked on. I also added a safety STOP switch and a box for the spare pins etc.

Underside of the holding board
The wood to be carved (in this case a back) will be stuck into place onto the top of the holding board with double-sided tape and the template (in fact a mirror image) is mounted on the underside with fixing bolts. The template set corresponds to each of the contours on Andrew Mowry's plan. In order to engage with the pin properly each plywood contour was 5mm deep. I found that four of these could be stacked and glued together for convenience.

The idea will be to start with the pin fully retracted and take the thickness down to 17mm. Then the pin is raised by 5mm, and the router cutter is lowered to 16mm and the first contour is cut. Then the cutter goes down to 15mm and the pin up another 5mm and cut again...and so on.

Now to see if the theory works out in practice!

Arching Template sets

1 comment:

Peter Brown said...

Clever! Let's see those chips fly!