How to Sharpen Lawn Mower Blades

Updated on October 25, 2018
Anthony Altorenna profile image

Anthony enjoys spending time in the workshop, the kitchen, the garden and fishing. Many of his featured projects can be seen in his yard.

A sharp mower blade cuts cleanly
A sharp mower blade cuts cleanly | Source

A Sharp Lawn Mower Blade For A Clean Cut

A sharp lawn mower blade cuts cleanly for a professional, finished look to your yard and improves the health of the lawn. Dirt, sand and debris can quickly dull a lawn mower blade, even when used on a near-perfect lawn. A dull blade tears through the grass, leaving ragged edges that are more susceptible to pests and disease, and gives your lawn an uneven cut.

Cleaning and sharpening a lawn mower blade is very easy and takes only a few minutes. To make the job even easier, purchase a spare blade for your mower and rotate blades every few weeks, swapping out the dull blade for a pre-sharpened replacement. A clean and sharp lawn mower blade provides a clean cut for a great looking and a healthy lawn.

After all of the time and money spent on fertilizer, watering and weed control, spend an extra couple of minutes to sharpen your lawn mower blade. Your grass will thank you!

How to Sharpen a Lawn Mower Blade

Remove the Mower Blade

The first step in sharpening a lawn mower blade involves removing the blade from the mower. Before attempting to remove the blade, disconnect the spark plug wire to prevent the mower from starting accidentally. Also, drain the gas tank to avoid spilling fuel on your lawn or driveway. With the spark plug disconnected, turn the mower on it's side to expose the blade and the retaining hardware.

Using a block of wood as a wedge to hold the blade in place, remove the retaining bolt with a socket or large wrench (my Toro mower uses a 7/8" socket). Some mower models have three bolts which must be removed. If the bolt is rusted on or is especially tight, slip a short section of pipe over the ratchet handle; the longer handle provides additional leverage for removing stubborn nuts and bolts.

Before removing the blade, take note of the blade's orientation and the retaining bracket and washer. Most lawn mower blades have distinctive "top" and "bottom" sides, and the blade must be re-installed in the proper orientation.With the blade removed, use a penetrating oil such as WD-40 and a rag to clean both surfaces of the blade. Inspect the cutting edges carefully; in most cases, the blade will be dull and worn with just minor nicks along the edge. If the blade is noticeably bent or if the cutting edge is suffering from deep dings, the edge may need to be professionally re-ground or possibly replaced.

Removing the lawn mower blade
Removing the lawn mower blade | Source

Working the Edge

In most cases, just a light sharpening is all that is needed to increase the cutting efficiency of the blade. Using a fine-tooth metal file (designed for use with metal), clamp the blade securely on a workbench and lightly file the cutting edge. Take care to follow the established bevel of the blade, and use light but firm strokes. Start the stroke in the center of the blade and work outwards.After a few strokes, flip the blade over. The filing process creates a "burr" or ridge on the backside of the blade. With a few light strokes, remove the burr from the backside of the blade to reveal the sharpened edge. Repeat this process on the other cutting edge of the blade.

A drill or rotary tool, a rotary sharpening stone is a good alternative to the metal file, especially if the blade is very dull or has a few dings on the cutting surface. With the rotary sharpening stone spinning at the tool's higher RPMs, a few light passes along the cutting edge will quickly restore the blade's sharp edge (you still have to remove the bur from the back side of the blade to create the sharp edge). A grinder is another alternative, though this removes a lot of material and is harder to control than either the metal file or rotary sharpening stone. But if the blade has large dings, a hand-held or bench grinder may be the best option to restore the blade's edge.

Use a file to sharpen a dull mower blade
Use a file to sharpen a dull mower blade | Source

Balancing Act

After sharpening both ends of the blade, it is important to ensure that the blade is balanced. An unbalanced blade spinning at high speeds can damage the mower's motor and is dangerous to the operator.

To determine if the blade is balanced properly, simply hang the blade on the wall from a nail, supporting it in the middle. A balanced blade will sit level to the ground or workbench. I used a small triangular block to check the lawn mower blade in the photo for proper balance. If the blade is unbalanced and tips to one side, make a few light passes with the file on the side of the blade that is tipping downward, and try again.

The Finished Cut

Consider purchasing a spare blade for your mower. Keeping a spare mower blade sharpened makes it quick and easy to swap out the dull blade for the sharpened spare and quickly gets you back out and cutting with a sharp blade. Later, sharpen the first blade and wipe it with the penetrating oil, and then store the blade until its time to swap the blades again.

I usually swap my blades every few weeks - or when the mower's cut leaves random blades of grass standing tall.

How to Sharpen a Lawn Mower Blade

Still not sure how to sharpen a lawn mower blade? Take a few minutes to watch this video, and see how easy it is to sharpen your own lawn mower blade. Why pay someone else to do a simple chore that you can do yourself?

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How to Kill Nutsedge

Nutsedge may look like grass, but it is an aggressive weed
Nutsedge may look like grass, but it is an aggressive weed | Source

Rid Your Lawn of this Invasive Weed

Product Review: Ortho Nutsedge Weed KillerNutsedge is perennial grass-like plant that spreads by seed or through underground rhizomes and tubers. Its three-side stalk easily identifies nutsedge as a member of the sedge family. Pluck a stalk from the ground and gently roll it between your thumb and forefinger. If the plant is a nutsedge, you will feel the triangular shape of the stalk.

Once established in a lawn, nutsedge spreads quickly and aggressively during the warm summer months, and is very difficult to control. Within a few days of mowing the lawn, the bright yellow-green nutsedge leaves grow above the rest of the grasses. As the cold weather approaches, leaf growth slows and the nutsedge seems to disappear among the blades of turf grass. But it is still there, going dormant for the winter and getting ready to burst forth in greater numbers in the following spring.

Nutsedge plant
Nutsedge plant | Source

There are two types of nutsedge found commonly in lawns and garden beds throughout North America: Yellow Nutsedge and Purple nutsedge. The two plants closely resemble each other and though I think the invader in my front yard is the Yellow Nutsedge variety, I'm not really sure. It doesn't really matter if it's yellow or purple; it was spreading quickly and I wanted it gone.There are several products available that claim to kill nutsedge. I tried a couple of different general lawn care products that target weeds, with different levels of success. However, the nutsedge seemed too tough for the general-purpose weed killer that targets the pest plant but leaves the grass alone.

Then, a friend suggested Ortho Nutsedge Killer for Lawns so I ordered a couple of bottles. This product comes premixed in a small spray bottle and applying the Nutsedge Killer is as easy as spraying the offending plant with the lethal liquid. Coverage is somewhat spotty, and I used about a bottle and a half to spray about a ten-square foot area plus hitting several isolated little nutsedge islands that popped up here and there around the lawn.

The impact was almost immediate and within 48-hours, the nutsedge was already turning brown and starting to wilt. This isn't a guarantee that Ortho Nutsedge Killer will work for you but if you are trying to control this botanical pest, buying a bottle or two seems like a small risk. I'm sure that I'll need to buy more in the future, because nutsedge is a tough perennial and there are still lots of little tubers just beneath the surface that are waiting for their turn to sprout. If too many do, they'll get hit with a dose of Ortho Nutsedge Killer.

Our freshly mowed lawn
Our freshly mowed lawn | Source

Questions & Answers

    © 2012 Anthony Altorenna

    Tell Us About Your Lawn Care Tips

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      • Cooper Goldie profile image

        Cooper Goldie 

        6 months ago

        Great tips. I know people that just buy a new blade each year or two which is just a waste of money. Everyone who regularly mows should learn to sharpen their blade.

      • Gypzeerose profile image

        Rose Jones 

        5 years ago

        I am trying to replace my lawn, but we still have to mow. This info on sharpening the blades is helpful.

      • profile image

        beindustrial 

        6 years ago

        Lots of great information in this lens! We do have a rotary mower at home and sharpening it is in deed very tricky, fortunately I found a site that provides step by step DIY lawn mower maintenance stuffs. If I can remember it well the site's name is lawnEQ.

      • Frugal-UK LM profile image

        Frugal-UK LM 

        6 years ago

        great lens

      • Srena44 profile image

        Srena44 

        6 years ago

        great lens

      • profile image

        anonymous 

        6 years ago

        Thank you for this information! We have a lawn mower that works great except the blades aren't very sharp anymore which makes lawn mowing a difficult task. My husband loves taking things apart so he'll be excited that I found this, and I'll be excited to have the mower working better. Thanks again!

      • profile image

        pawpaw911 

        6 years ago

        Great how to lens, step by step with photos. Balancing is very important. Seeing the reel type mowers reminded me of trying to use one, when I was a kid.

      • profile image

        bulululu 

        6 years ago

        great lens thanks for share push lawn mower

      • BLouw profile image

        Barbara Walton 

        6 years ago from France

        Pounced on this with glee as no longer have my geese to help me mow the lawn, but fell at the first gate. I need MUCH more inf! Where is the spark plug? What does a spark plug look like? How do you drain the fuel? Syphon it off? Do leave a message on my page as I think I'll need to know how to sharpen the blades of my mower soonish.

      • profile image

        mockingbird999 

        6 years ago

        I should do this myself. It would save a few bucks.

      • profile image

        anonymous 

        6 years ago

        Stopped back to post this to +1, because this is helpful information for anyone with a lawn mower. You know! :)

      • profile image

        Halcyon100 

        6 years ago

        This is great - as someone into their lawn tractors this lens is much appreciated as it reminds us all how important it is to have sharp blades when cutting grass

      • GOT LM profile image

        GOT LM 

        6 years ago

        Nice work.

      • profile image

        sellhousefastusa 

        6 years ago

        My brother can use this info will refer him to this lens as well

      • TonyPayne profile image

        Tony Payne 

        6 years ago from Southampton, UK

        Excellent advice and tips. Our electric mower is about a year old now, and it's probably time to look at the blade and to get it sharpened. I might just take your advice and buy a spare blade, so I can sharpen the spare one more easily. Even though our lawn isn't that big, it does pay to have a sharp blade. Nicely done, blessed.

      • profile image

        anonymous 

        6 years ago

        Anthony, you've done it again...created a DIY that will be so helpful to so many people and you make sharpening a lawn mower blade so very interesting with your little tips and insights from experience along the way. I especially love how you always emphasize safety...removing the spark plug to prevent a start is excellent. I think many a person has faced that orientation issue and that is such good advice (no swearing required). I love your balancing act and advice on the burring...first timers will love that. A good way to drain the tank is to mow until the lawn mower runs dry but that is another point that is so very important, no one want to clean up spilled gas. I notice that you have notched your wood block to stabilize the blade...of course!

      • Lady Lorelei profile image

        Lorelei Cohen 

        6 years ago from Canada

        There are times when I definitely appreciate being a woman. My husband gets to take care of cutting the grass and sharpening the blades on the lawn mower.

      • squidoopets profile image

        Darcie French 

        6 years ago from Abbotsford, BC

        Very nice tutorial for sharpening lawn mower blades, many thanks

      • profile image

        JoshK47 

        6 years ago

        Quite an awesome, insightful guide you've put together - blessed by a SquidAngel!

      • profile image

        anonymous 

        6 years ago

        Pretty handy tips on DIY as always!

      • flycatcherrr profile image

        flycatcherrr 

        6 years ago

        Ooh, nice tip about checking the balance by hanging the blade from a nail - useful to know! My lawn is a former hayfield, death to mower blades. :S

      • Diana Wenzel profile image

        Renaissance Woman 

        6 years ago from Colorado

        Excellent tutorial, as always. Appreciated! Right now I don't have a lawn to mow, as my acres are all natural desert terrain (mostly sagebrush, cacti, wildflowers, native grasses, and pine trees). One day, though, this learning will come in handy. Thanks.

      • Ahdilarum profile image

        Ahdilarum 

        6 years ago

        Great insight about lawmaker maintenance. Liked this lens..

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