Best Lawn Mower Blade Sharpener  - Lawn Tool Guides
It's a no frill's blade sharpener that's the best grinding wheel to sharpen lawn mower blades whilst still on the mower. Stick it in a cord or cordless drill and run it along the blade. The preset angle of the stone aligns with the blade and it grinds a new face. Being so cheap has limitations such as getting the correct angle evenly.