Lawnmower blade balancer

Balance your lawnmower blades using this simple tool. Additional parts required are two standard 608zz skateboard bearings, two #4 x 1/2" screws, two 12.5x5 mm rare earth magnets and a M8x80 hex cap bolt. There are multiple blade holders published with this thing. One fits John Deere (splined) mower blades, and the other is for blades with the standard 16 mm (5/8 inch) sized hole. The SketchUp file is included for making your own blade holder.

example magnets: http://www.kjmagnetics.com/p