Not much to this.  I bought a drill press from a pawn shop. I adjusted the belt to the slowest rate 600 rmp. Then took the stand off , turned it upside down. I made a sanding disk by cutting a 3/4" circle. Drilled a hole in the middle, inserted a bolt, glued it. Then to make a perfect flat surface I cut a piece of glass the same size. Glued it down with heavy coating of contact cement. Dulled the edges. I use spray glue to temporaly glue sandpaperon the flat surface. One other thing I did was add a foot switch . This enables one to to hold the metal then start the the machine,sand and turn it off without lifting the metal. The reason this is important is it is impossible to stouch and remove it without curving the edges of the metal.