Your membership has expired

The payment for your account couldn't be processed or you've canceled your account with us.

Re-activate

    How to Remove and Replace a Lawn Mower Blade

    This simple project will keep your walk-behind mower—and your lawn—in peak condition

    The best cut comes from a sharp lawn mower blade, so it’s key to sharpen it a few times each season. And it’s worth learning how to remove the lawn mower blade yourself.

    You’ll need to do this, of course, if you want to sharpen the blade yourself. But even if you have a professional do it—which is what we recommend—you’ll save money by removing the mower blade from the deck to bring to the shop rather than delivering the mower with the blade inside.

    For instance, Cary Mower & Saw in Cary, N.C., told us it charges $8 to sharpen a blade removed from the mower deck and $30 for a blade that’s still inside the mower deck.

    What’s so crucial about sharpening your lawn mower blade? For one, a dull blade damages your grass by creating a ragged cut. That can lead to bare patches and other eyesores as well as invite disease. A dull blade also stresses the lawn mower’s motor, making it work harder. That means your mower will use up more battery power or gasoline per cut.

    While we recommend a few honings per season, your lawn mower blade might need more if you have rocky soil conditions or extra-tough turfgrass. When in doubt, inspect the lawn after mowing. If the grass blades have a lot of split ends instead of being cleanly cropped, you probably have a dull blade. Brown-tipped grass blades are another giveaway.

    More on lawn mowers

    The actual sharpening is best left to the pros at your local hardware store or power-equipment shop, who might charge $7 to $10 per blade. It’s a good idea to own an extra blade so that you’ll have a sharp one handy when the other goes in for servicing.  

    Here’s how to remove the lawn mower blade from your walk-behind mower in five steps. If yours is a gas mower, tackle the project after running the mower dry or siphoning out the gas (a turkey baster works as well) to prevent a fuel spill when the mower is tipped on its side.

    Step 1

    Make sure there’s absolutely no way the engine can jump to life. With a battery mower, remove the batteries; with a gas mower, remove the spark plug. Then turn the mower on its side. With a gas mower, you’ll want the air filter facing up to prevent oil from saturating the filter.

    Step 2

    Put on heavy work gloves so the sharp blade doesn’t cut you. Secure the lawn mower blade by lodging a 2x4 block between it and the mower deck (a C-clamp can help hold it in place if needed). Then use a wrench or socket to loosen whatever fasteners are anchoring the blade to the drive shaft. There may be one bolt or two, with or without special washers.

    Step 3

    Once you’ve removed the blade assembly, take a picture of it with your phone so that you know the right way to put all the parts back together. (Your owner’s manual should also have a drawing of this.) Then take the lawn mower blade into a shop for sharpening.

    Note that if you’re an advanced DIYer, you could try sharpening the blade yourself using a metal file or a bench grinder. John Galeotafiore, who manages outdoor power equipment testing at Consumer Reports, says that if you already own a Dremel rotary tool, that brand’s Lawn Mower & Garden Tool Sharpener attachment can help in sharpening the blade. It’s available online, in hardware stores, and at home centers for about $15.

    Step 4

    Put the blade assembly back together, following the picture you snapped earlier. It’s important that the blade’s cutting edge follows the direction of rotation. The wings of the lawn mower blade will be oriented up toward the mower deck, and any writing on the blade will likely be facing away from the deck. If the blade bolt comes with a washer, its concave side will be facing the blade.

    Step 5

    Once you’re ready to tighten the bolt, put the work gloves back on. Reinsert the wooden block—on the opposite side of the mower deck this time—and tighten the bolt using a combination wrench.    

    Some manufacturers recommend using a torque wrench for this task because overtightening a bolt could cause it to crack, while undertightening it could allow the lawn mower blade to fly off while the mower is running.           

    Before flipping the mower back upright, take a few minutes to clean out the underside of the deck and apply a light coating of silicone spray, if you have it. This will prevent the built-up clippings from compromising airflow. Along with a sharpened blade, that measure could make the mower more energy-efficient while keeping your lawn and your lawn mower in tip-top condition.

    If your mower is beyond repair, check our full lawn mower ratings and recommendations.


    Tobie Stanger

    I cover the money side of home-related purchases and improvements: avoiding scams, making sense of warranties and insurance, finding the best financing, and getting the most value for your dollar. For CR, I've also written about digital payments, credit and debit, taxes, supermarkets, financial planners, airlines, retirement and estate planning, shopping for electronics and hearing aids—even how to throw a knockout wedding on a shoestring. I am never bored. Find me on Twitter: @TobieStanger