i have worked as a fleet equipment tech for 30 years and would advise not to sharpen these blades the sand we have here in florida eats the blades pretty bad,if you sharpen a worn blade you risk damage to the bearings in gearbox its called balance you grind off metal you change balance (take a blade off your ceiling fan and see what happens) why not change the blades its a lot cheaper than bearings and gearbox repairs and other peoples body parts