How do I sharpen my rotary lawn mower blade?

Updated June 29, 2018

Lawnmower blades need occasional sharpening to cut the lawn cleanly without ripping or tearing the blades of grass. A rotary lawnmower has five blades that curve forward. The blades rotate forward when the mower pushes forward so that two blades touch the ground at all times to cut the lawn. A rotary mower sharpening kit includes a crank handle, a paintbrush and sharpening compound.

Place the rotary mower on a flat surface on its side with one tire pointing up. A workbench works well to prevent bending over.

Wipe the centre of the tire pointing up with a towel to remove any grass, dirt or debris.

Place needle-nose pliers on the C-ring in the centre of the wheel. Grasp the C-ring tightly with the tips of the pliers and work the C-ring out by wiggling it from side to side while pulling straight out at the same time. Set the C-ring aside.

Grasp the wheel with both hands. Pull it straight up to remove it and set it aside.

Grasp the black gear with one hand and pull it straight up to remove. Set the gear aside.

Place the crank in the rotary mower sharpening kit onto the metal tube behind the gear area. The crank allows blades to turn backward for sharpening.

Dip the paintbrush from the sharpening kit into the sharpening compound. Apply a generous amount to the front cutting edge of all five blades.

Turn the crank toward the lawnmower handle to spin the blades backward. The first few cranks will meet with resistance if the blades are very dull, but then the crank becomes easier to turn. The blades sharpen with this action due to the sharpening compound striking the solid metal plate at the rotary mower bottom.

Turn the crank in the same direction for 20 minutes and take breaks as needed to rest your arms.

Spray any remaining sharpening compound off the blades with medium force, using a garden hose.

Pull the crank straight up and off the lawnmower and slide the black gear on the mower.

Place the wheel over the gear and slide it straight on the axle.

Push the C-ring into place to hold the wheel on the mower.


Spray a generous amount of spray lubricant to the wheel if it is stubborn and will not pull off easily. Use a workbench or tall counter to avoid back fatigue when sharpening rotary lawnmower blades.


Do not place hands or fingers near mower blades when sharpening them.

Things You'll Need

  • Towel
  • Rotary mower sharpening kit
  • Needle-nose pliers
  • Rubber mallet
  • Garden hose
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About the Author

Mary Lougee has been writing for over 10 years. She holds a Bachelor's Degree with a major in Management and a double minor in accounting and computer science. She loves writing about careers for busy families as well as family oriented planning, meals and activities for all ages.