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?

This is what disc sanders are for. I'm talking about the stationary machines
with a table.

One trick you can do is jury-rig the same thing using your belt sander. Clamp
it on its side to a workbench. Then clamp a piece of plywood to the table. Make
sure it is 90° to the belt. Turn the belt sander on and use both hands to move
your oval sign against the sander.

Dan

"designbysue" wrote in message
m...
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?

"designbysue" wrote in message
m...
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?


rec. woodworking might be better. If you cut with a trammel point you
should get pretty good circularity. A bandsaw with a jig would do better,
as would a router. If you know someone with a good disk sander, a circle
jig similar to the bandsaw jig also works. Does for me, anyway.

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?


In addition to a stationary disk sander, you can also do this with a
spindle sander or a sanding drum chucked in a drill press.

~Mark.

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?


i would suggest using a drum sander, you simply put in a pillar drill
and sand away.
Good luck

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!

Thank you for your responses. The piece is 5 feet by 3 feet so
working with the piece is very difficult, expecially with the small
equipment I have. I used my belt sander manually and got a decent
edge.