I thought that a disc sander would be a useful addition to the shed, so bought a 2HP 240V motor off E-Bay (1440RPM), a small sheet of 1/2" ply and an off cut of 3mm metal sheet. Went out and bought a really old basic wood lathe just for the parts ($15) as it had a couple of small face plates and then cut up the frame and threw the rest out apart from the motor.
Cut the sheet of ply into 2 circles of 350mm and glued them together. Coated the ply with Polyurethane to seal the ply. Bolted the faceplate to it and then machined it on the metal lathe to a perfect circular disc and also the front face to make it flat, re-coated the front face with polyurethane. Then went on to build a dust extraction frame and another frame holding the table.
Full build details are located at:
Made a 350mm Disc Sander | MIG Welding Forum