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Step-by-step instructions to keep your riding mower blades running at their best
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Keeping the blades sharp and in good condition on a riding lawn mower will increase fuel efficiency, give better mowing results, and extend the life of this expensive piece of lawn maintenance equipment. Here are steps and tips on how to do this project yourself.

  1. 1
    Check the condition of your mower blades to see if they need changing. If the blades are not significantly worn but are dull, they may only require sharpening. If, on the other hand, the airfoil built into the back of the blade is worn away, or the blade is bent or otherwise damaged, you probably need to replace it. [1]
  2. Park the mower on a suitable work surface. Turn it off and lock the brakes or chock the wheels. Disconnect spark plug(s). [2]
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  3. [3]
  4. You need to make sure it is supported solidly, as riding lawn mowers are heavy, and you don't want to risk having it fall on you while you work on it. For greater safety, consider using a manufactured mower or tractor lift. [4]
  5. Get the correct size wrench to fit the mandrel nut (or bolt) on your mower. You may also need a cheater pipe or other means of keeping the blade from turning while you remove the nut.
  6. 6
    Turn the nut (or bolt ) counterclockwise to remove it from the mandrel shaft, then allow the blade to drop off. For blades that are tightly seated, you may have to pry the blade off or work it up and down to loosen it after the nut is removed.
  7. Choose new blades to suit your own preferences – there are a number of different blades for each type mower, including enhanced discharging blades, mulching blades, and heavy duty blades. [5]
  8. Since there are many different brands and manufacturers of riding lawn mowers, making sure the blades you purchase fit your mower is critical for a successful project.
  9. Be sure to install the blade right side up , as they may fit upside down. Generally, if the blade has an offset in it, the center will be in a higher position than the ends of the blade. Make sure the blade fits all the way onto the spline to prevent damaging it when the nut that secures it is tightened. [6]
  10. You may have torque specifications for this step for your individual mower.
  11. Check the belts, pulleys , tensioners, and other parts of the mower deck assembly while you have the mower parked for servicing.
  12. 13
    Lower the mower off the blocks, and clean up/put away your tools.
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Expert Q&A

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  • Question
    How do you know when your lawnmower needs a new blade?
    Grant Wallace
    Landscaper
    Grant Wallace is a Landscaper and Owner of Grantlanta Lawn in Atlanta, Georgia. With over seven years of experience, he specializes in lawn maintenance and landscape installation. In 2012, he earned his BA from the University of West Georgia. Grant has been profiled in Shoutout Atlanta, Canvas Rebel, and Voyage ATL.
    Landscaper
    Expert Answer
    Unplug the spark plug from the lawn mower motor and gently run your finger along the blade. If it feels dull and rounded, it needs to be sharpened.
  • Question
    How often should change blades on a mower?
    Grant Wallace
    Landscaper
    Grant Wallace is a Landscaper and Owner of Grantlanta Lawn in Atlanta, Georgia. With over seven years of experience, he specializes in lawn maintenance and landscape installation. In 2012, he earned his BA from the University of West Georgia. Grant has been profiled in Shoutout Atlanta, Canvas Rebel, and Voyage ATL.
    Landscaper
    Expert Answer
    It depends on how often you use your mower—for instance, residential homeowners who only mow their grass a couple of times a month only need to sharpen their mower blades once or twice a year.
  • Question
    If I have two blades and need to replace one but the other is fine, is it best practice to replace both?
    Community Answer
    It is. As long as you are changing one, change them both for a smooth cut.
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      Warnings

      • Make sure blades are properly fitted on the mandrel so they do not slip or come loose.
      • Block the mower up solidly so it will not fall while working underneath it.
      • Mower blades have sharp edges, and with worn out blades, almost any edge can be sharp, not just the cutting edge.
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      Things You'll Need

      • New blades
      • Wrenches
      • Block to support the mower

      Expert Interview

      Thanks for reading our article! If you'd like to learn more about changing the blades, check out our in-depth interview with Grant Wallace .

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