Whenever I've used my Roto-Zip to cut figured patterns in plywood I've
always been frustrated with how much splintering of the bottom edges of the
cut line occurs. The other day I tried something new to reduce this problem
and it works really great.
I used a sheet of foam insulation as a backer to the 1/4 inch plywood that I
was cutting. I set the depth of cut so that the tip of the Roto-Zip blade
cuts into the foam, but doesn't exit the bottom of it. The foam insulation
holds the edges of the cut line and almost totally eliminates the chipping
of the bottom side of the plywood. The foam also collects and holds much of
the sawdust, and it doesn't seem to foul the Roto-Zip blade. It also allows
you to put the whole project on top of the workbench and not have it hanging
off the edge to allow for the blade protrusion from the bottom, so you don't
have to worry about hitting your workbench with the blade. You can also
re-use the foam panel many times before it gets so many cut lines in it that
it's effectiveness is reduced.