Disconnect the spark plug wire (gas) or remove the battery (electric)
Tilt the mower back so the air filter/carburetor side is up (gas) or follow the manufacturer’s tilt guidance
Remove the blade bolt/nut using a wrench/socket
Remove the blade
Secure the blade with a clamp in a vise
Note the blade’s cutting edge orientation and existing bevel
Use a bench grinder or angle grinder with a metal grinding disc
Sharpen the cutting edge using light, even passes following the original bevel angle
Grind until the nicked/dull edge is removed and a consistent sharp edge is formed along the full length
Avoid overheating the blade; pause as needed
Clean off burrs and sharp edges with a file or deburring tool
Check blade thickness and condition; replace if cracked, severely worn, or bent
Balance the blade using a blade balancer
Remove material from the heavier side until balanced
Reinstall the blade in the correct orientation
Tighten the blade bolt/nut to the manufacturer’s specified torque
Reconnect the spark plug wire or reinstall the battery
Test run briefly on a flat surface and check for smooth cutting performance