Making Dished Work Boards
Copyright ©1999 Howard Coleman
Why are dished work boards needed?
Accurately dished work boards are useful as gluing cauls for
supporting the top and back of a guitar during construction. They
are also useful as sandpaper supports to produce complementary
arches on the sides. These arches, being spherical, should reduce
localised stress in the top and the back by distributing it more
evenly than other methods. They therefore offer a significant
improvement on the old method of gluing curved braces on to
panels to arch them one way and then bending the panels at right
angles to this over a hump in the profile of the sides to achieve
a three-dimensional arch.
How I make them
This is definitely a job where a dust mask is needed.
You are going to look like a snowman by the time you finish this!
Ear and eye protection go without saying. I start with 55cm
(21½") discs cut from medium density fibreboard (MDF) of 18
mm (3/4") thickness. I use a router to remove material from
the surface of the discs. This is guided by a special jig (plans here; photo here) with a choice of guide rails
for arches of different radius. The curves on the guide rails are
marked out with the help of a spreadsheet.
The jig straddles the disc and the router is slid along the guide
rails which allow it to cut deeper at the centre of the disc. The
jig is then rotated a little around the disc and the operation
repeated until the whole disc has been dished. Any slight surface
imprefections can be removed easily with a scraper.
Last revised: October 25, 2000.
