An apparatus for sharpening blades, such as those used for mowing. A rotary grinder is mounted within an extensible, retractable, and rotatable support assembly. Lockable, rotational adjustment of the position of the grinder about three axes, and translational movement along one axis is thereby provided. A spring attached to one end of the assembly counter-balances the weight of the grinder. An adjacent blade holding fixture maintains the workpiece at a predetermined angle for grinding. A toggle clamp, edge alignment keepers, and a registration pin secure the blade in place. An adapter fixture, including a toggle clamp and an alignment recess, attaches to one end of the blade holding fixture. The adapter fixture has an angled shelf to orient and secure smaller, contoured blades requiring a different edge grinding angle. Once the support assembly is adjustably secured, the grinder is moved along the cutting edge of the blade for sharpening.