I made this one day when I wanted it right away for a project I was working on.
I used standard paper backed 9×11 sheets of 180 grit that I had on hand. Ideally you should use cloth backed sandpaper if you want it to last longer. I cut 5 sheets into 2 ¼” x 5 ½” pieces with some tin snips.
Sandwich them all in between some 3/8” thick plywood (don’t use ¼” because it will break apart).
I cut slots ¼” apart and 1 3/4” deep on each end. Use a scroll saw for this because you will end up ruining the blades and the scroll saw blades are inexpensive.
Drill a hole in the center for a 2 ½” long bolt (use at least a 5/16” bolt). Using a 1 ½” hole saw, I made 6 wooden washers from 1/8” Masonite. Stack the sandpaper back to back, staggering the direction 45 degrees for each set of 2 sandpapers. Put a washer in after every 8 sheets of sandpaper.
Bolt it tight.
It works good for sanding irregular shapes