On Thu, 15 Jun 2006 05:42:56 GMT, lid (designbysue) wrote:

Hoping this is a good place to ask - I have to make an oval sign out
of 3/4 MDF. I am using a jig saw to cut the basic shape. My
question is what is the best tool to sand to the finish shape? If I
use a belt sander or orbital sander, I can get the shape, but the
edges are not perfectly 90 degrees to the surface. Is there a tool
that I could use ( or a jig for a tool) that would finish the edge to
a 90 degree angle?

Hi there-

Using a sander to do this is not the easiest way to go... If you've
got a router, the best thing to to is to cut the oval out of 1/4"
plywood or mdf (even thick plastic can work) and get it to the size
and shape you like (it's a whole lot easier than the full 3/4" piece)
and then use that as a template. Rough cut your MDF as you already
have, leaving 1/8" or so all around, and then clamp or screw your
template to the finished piece(and the edge of a workbench) and use a
flush trim (straight bit with a bearing on the bottom) or pattern bit
(straight bit with a bearing on the top) to finish the edge of the
MDF. Just set the router so that the bearing rides on the template
you made from the thinner material, and the cutting edges are shaving
the MDF. This should give you a very nice finished cut that is
perpendicular to the surface of the material, and there isn't any
trial and error or need to develop a "feel" for it on a sander.

The added bonus to this approach is that if you need to make more than
one, either now or later on, you'll be able to make perfect duplicates
as long as you have the original template.

Hope this helps!