[cooperino]

Originally Posted by J-Mech

I've never, ever balanced a mower blade after sharpening. The other day, I sharpened my blades. When I got done, I thought, "What the hevk, let's see how balanced they are.". So, I hung them on a screwdriver and set the blade horizontally. Never moved. Gave it a bit of a spin.... always just randomly stopped. Guess it isn't that hard to keep them "balanced".

With a good eye sharpening should not throw them out too bad. But altering the way the OP was could easily throw them out of balance.