I recently decided to go through all of my ukuleles and replace the synthetic nuts and saddles with bone ones. After going through two of them, my fingers are just in too much pain from shaping them from blanks. I know belt sanders can be had for $40 these days but I just wanted a small sander to work with these nuts and saddles.
So I designed this little Dremel (mine is a Dremel 300-1) holder and table to do just this with a grinding stone or sanding band adapter. And it works great!
Be sure to print the table upside down to keep the top of table as flat as possible. The Cura screenshot will show my settings but I might up the infill a bit. I designed this so there's really not much pressure on the structure while sanding (since you're pushing against the Dremel and not onto the table or stand) so mine works fine in PLA.