Making the Fixture
I have taken the basic idea presented there and
adapted it slightly. Instead of using angle aluminum stock, I have used
square stock because it is more rigid. I have had problems finding
absolutely straight angle stock. It tends to flex easily which means a
straightedge is needed to ensure it is bolted to a board or clamped down
while keeping the sanding face true.
rigidity of the square aluminum keeps it straight.
Another way to do it would be to route a lip on a piece of particle board
and use wood screws to hold a piece of angle stock in place. If the
routed lip is straight, then the angle can be pushed against it to ensure it
is also straight.
Use a good grade of sandpaper, such as the new paper
made by 3M called Sandblaster. Good sandpaper will mean you do not have to remove the angle
I often use 48" stock
so I made the jig 5' feet long. But it can be as long as
you like. I simply clamp the jig in place on my bench
for use and when I am finished it can be put in a corner out of the way.
A sheet of sandpaper is cut into strips and
spray glued to the aluminum. Clean the aluminum with solvent or
alcohol before applying glue. Also be sure to spray both the
back of the sandpaper and the aluminum. Allow the glue to become tacky
before adhering the sandpaper.
Alternatively you can use sticky-back sandpaper
that comes in rolls. I really do not like this stuff because it tends
to be thick and wavy and does not like to stay down. If the sandpaper
is not flat on the block then it is not able to sand straight or flat.
A push block is needed to provide even pressure
on the sheet stock so that it sands evenly. Most sheet can flex easily
across it is width so using your hands will probably result in a bowed edge
rather than the straight edge needed.
What is not shown here is that the corners of
the aluminum are rounded slightly. The sheet will be radiused along
the edge unless a board of some type is placed against the aluminum to raise
the sheet up from the radiused corner. I use a scrap piece of masonite
because its smooth surface allows the sheet to slide easily. A piece
of smooth particle board would work just as well.
Caution! Be sure that the
bottom of your push block and the surface that you are sliding the sheet on
is free of any grit that will gouge the sheet.
I tried using my T-Bar sanding blocks as push
blocks but even with coarse paper they kept slipping. My solution was
to use a piece of scrap 1 x 4 with several pieces of sandpaper on one side
of it to grip the sheet stock. On the other side I used polyurethane
glue to attach a 1 x 2 handle. It is not pretty and it is not too
flat either, but it does not really need to be as long as it can grip the
sheet fairly evenly.
I tested the jig by sanding a stack of six 3/32
x 4 x 48 balsa sheets and I finished the whole stack in about the same time
it would have taken me to do one or two sheets using my previous method.
All the sheets matched up extremely well.