I prefer using my 1"x 42" sander-grinder to grind plane blades and chisels. My low-tech method provides the same results as a regular-wheeled grinder, minus any expensive attachments. The belt also seems to run cooler than a wheel. This reduces the risk of accidentally overheating the edge and ruining the tool. This method can be easily adapted to fit a disc sander.
Starting with a 1-1 ¼" thick piece of scrap, miter one end to 25˚. Next, adjust the sander’s top so that it’s perfectly perpendicular to the belt. Clamp the block to the table to match your sharpening needs.
To grind a fresh 25˚ bevel, use a square to make sure that the guide block’s edges are perpendicular to the front the table. Alternately, you can rotate the block to match a completely different angle. To do this, simply touch the bevel against your belt before clamping your guide block.
Be aware that grinding does produce some sparks. If you use your sander for wood, be sure to clean out any sawdust before doing any metalwork.
