I make a lot of wooden toys and find my disc sander indispensable for both shaping and smoothing small parts. Unfortunately, this calls for the use of both coarse and fine discs, and I have only one disc sander. My solution is to mount both #80-grit and #150-grit paper to the disc at the same time. A circle of one grit is attached to the center of the sander’s platen, while the other grit surrounds it as a ring.
To make the discs, I stack two sheets of standard 9″ x 11″ sandpaper upside down on a scrap panel. Using a compass, I mark out a 41⁄2″-diameter circle within a 9″ circle, then knife through the lines. I stick one set of these perfectly matched discs to my sander’s platen. When the sandpaper wears out, I simply replace it with the complementary set of sandpaper.