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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.

Steps Download Article

  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. 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]

  3. 3

    Raise the mower deck to its highest setting to make it easier to access the blades. [3]

  4. 4

    Raise the mower itself to allow room to get your tools underneath it. 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. 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. 7

    Take the old blade to a hardware store or mower repair shop to match it with the new blades you will install. 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. 8

    Compare blades at the store to make sure the offset, spline (if applicable), length, and other features match. 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. 9

    Install the new blades on your mower. 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. 10

    Tighten the nuts that secure the new blade. You may have torque specifications for this step for your individual mower.

  11. 11

    Check the belts, pulleys, tensioners, and other parts of the mower deck assembly while you have the mower parked for servicing.

  12. 12

    Lubricate the mandrel bearings and other parts equipped with grease fittings before lowering the mower.

  13. 13

    Lower the mower off the blocks, and clean up/put away your tools.

Add New Question

  • 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.

  • Question

    My wrench set only goes to 7/8ths, and the nuts on the top and bottom are bigger. Where can I get bigger wrenches?

    Community Answer

    At your local tool shop. They are more likely to have the size, but if you don't want to pay that price, garage sales and flea markets might have the size you need for a low price.

  • Question

    The nut turns but do not loosen or tighten, what do I need to do?

    john Doe

    john Doe

    Community Answer

    Use a longer leverage pipe, make sure the pulley is not rotating, be sure spark plug wire is off the spark plug to avoid dangerous engine start, as the deck belt may turn the engine. If the pulley is turning when you try to loosen blade nut, get a friend to hold the pulley with vise grips or channel locks (not hands).

  • Question

    What do I do if my yard machine engine stops when PTO is engaged?

    Community Answer

    Make sure you're throttle is fully on; low throttle is hard on a mower engine.

  • Question

    I've replaced blades on a 42" deck before, blocked the blade, used a pipe for leverage but mandrel won't free from the blade. Blades are original on a 5-year-old machine. Any help?

    john Doe

    john Doe

    Community Answer

    They sometimes use a longer leverage pipe, make sure the pulley is not rotating, be sure spark plug wire is off the spark plug to avoid dangerous engine start as the deck belt may turn the engine. If the pulley is turning when you try to loosen blade nut, get a friend to hold the pulley with vise grips or channel locks - not hands.

  • Question

    How do I loosen the nut on my riding lawn mower blade?

    Community Answer

    Put a small block of wood between the blade and deck to prevent it from turning while you loosen the nut.

  • Question

    Which direction do I need to turn the nut that holds the blade on?

    Community Answer

    You turn the nut counterclockwise in order to loosen it.

  • Question

    What do I do if the bolts won't loosen to change the blades?

    Community Answer

    Go to Amazon and do a search for "lawn mower blade holder removal tool". You will want to kick yourself for not already having one. In the meantime, you can try putting a pipe on your wrench to get more leverage when taking off a tight nut.

  • Question

    How many blades are there on a rider mower?

    CurtM

    It depends on the model. Most riding mowers use a single long blade, but larger mowers sometimes use a pair of blades that may be anywhere from 6-32 inches (15-81 cm) in length.

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Video

  • Aftermarket blades are often much less expensive and of equal quality to original manufacturer's parts.

  • Sharp blades make mowing faster and more efficient, and extend the life of your equipment.

  • Make sure that the spark plugs are not connected.

  • Keep your lawn clean. Hitting debris shortens the life of your mower's blades.

  • When you have replaced the blade, keep the new one sharp; it will last much longer.

  • Some mowers have a parts list displayed on the mower itself to help select the right part for the job.

Thanks for submitting a tip for review!

  • 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.

  • Make sure blades are properly fitted on the mandrel so they do not slip or come loose.

Things You'll Need

  • New blades
  • Wrenches
  • Block to support the mower

References

About This Article

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