Direct Answer

To balance lawn mower blades, disconnect the spark plug wire and drain fuel for safety. Remove the blade by marking its orientation, then unscrew it carefully. Use a blade balancer tool or the gravity method (suspending the blade on a nail through its center hole) to identify which side is heavier. File material from the heavier side in small increments, retest frequently, and reinstall the blade with the marked side facing the same direction. Properly balanced blades eliminate vibration, ensure even cutting, and extend mower life.