How to Sharpen Lawn Mower Blades

Maybe you’ve been here before: You just finished mowing your lawn, but your grass still looks like a mess. It’s unevenly cut, it’s torn, it’s frayed at the tips–the cleanly sliced look you’re going for just isn’t there.

So now you have three choices:

• Mow it again and hope for a different result.
• Leave it as-is.
• Figure out what’s causing the problem.

Let’s be upfront here: The problem most likely isn’t you. We doubt you just forgot how to properly mow your lawn.

Instead, the problem is likely due to a dull lawn mower blade. As you use your mower over time, the blade dulls. Makes sense. But when that happens, your mower can damage your grass blades. To prevent that from happening, you must sharpen your mower blade. 

You can do this on your own or by using a service professional. In this blog post, we’re assuming you want to DIY the sharpening process. And if that’s you, we’ll tell you exactly how to do it. 

But first, let’s go a little deeper as to why you should sharpen your blade in the first place.

Why It’s Important to Sharpen Your Mower Blade

If you care about maintaining a beautiful lawn year-round, your lawn mower blade should be sharp enough to make clean, even cuts. In addition, a sharp mower blade:

• Makes you more efficient at cutting your grass
• Saves you money
• Promotes the overall health of your lawn

1. Efficiently Cut Your Grass

A sharper lawn mower blade can help you cut your lawn more efficiently. If this sounds far-fetched, allow us to explain.

You see, your mower’s engine has to work harder to cut the grass when it’s using dull blades, which means it guzzles more fuel. This also wears down other parts of your engine and can cause internal components to break while you’re mowing. As a result, a dull blade can actually decrease the life of your lawn mower. 

So, here’s why a sharp blade makes you more efficient at cutting your grass: 

• With a sharp blade, you’re less likely to need to stop to refuel your lawnmower in the middle of a mow. 
• With a sharp blade, your mower’s engine components are less likely to break down while cutting your grass.

2. Save Money

A dull blade can rack up unnecessary costs. If you strain your engine too much, you’re more likely to pay for repairs. And if you unnecessarily use more fuel, that’ll cost you, too.

3. Promote the Overall Health of Your Lawn

A sharp blade means clean cuts, which means your grass doesn’t sustain damage each time you mow your lawn. In other words, if you want to keep your lawn healthy, you must sharpen your blade from time to time. 

How Frequently You Should Sharpen Your Mower Blade

You should plan to sharpen your blade twice a season (or after every 25 hours of mowing). If you’re not sure when you last sharpened your blade, plan to do it before mowing again. Then sharpen it again later in the season. 

Here’s a sharpening-frequency guide you can follow for the year:

• Spring: Start the season off right by sharpening your blade before your first mow
• Summer: Sometime in the middle of the summer (say, June or July), sharpen your blade again. As your grass continues to grow, you’ll mow more often, which can dull your blade. 
• Fall: If you plan to mow fallen leaves, you may want to sharpen your blade before doing so. 
• Winter: If you spend 25 hours or more mowing over fallen leaves, sharpen it once more. Otherwise, take this season off.

The key point here is to get in the habit of sharpening your lawn mower blade multiple times a year.

The Steps for Sharpening Your Mower Blade

Now that you know why and how often you should sharpen your mower blade, it’s time to get to work. Follow these eight steps.

Step 1: Get Your Tools and Materials Ready 

Before you sharpen your blade, make sure you have the following:

• A pair of work gloves to protect your hands while handling the blade
• Protective eyewear to ensure dust and debris stay out of your eyes
• Spray paint or tape to mark the orientation of the blade before you remove it
• A block of wood to keep the blade in place while you remove and reattach it  
• Either a wrench or socket set to remove the blade from the mower
• WD-40 and a brush to help you clean gunk off the blade
• Either a dry rag or microfiber cloth to clean the blade (once any gunk is off)
• A vise to securely hold each blade while you sharpen it
• Either a hand file, power drill (with sharpening stone attachment), or a bench grinder
• Earplugs (if you use a bench grinder)
• A blade balancer to ensure the blade is balanced after you sharpen it
• A rust inhibitor spray to protect the blade after sharpening it

Step 2: Get Your Mower Ready

This might seem obvious, but it’s worth noting: Make sure your mower is off. Also, remember to disconnect the spark plug wire. Doing so prevents the mower from accidentally starting. Then transfer any gas left in the mower to a canister, so you don’t spill any fuel.

Step 3: Remove the Blade

Put on your work gloves and access the blade by carefully tilting the lawnmower to one side. As you do so, keep the air filter and carburetor facing up to prevent oil from spilling into these parts.

Next, keep the blade from turning by securing it with a block of wood. Then use a wrench or socket set to loosen the bolt or nut holding the blade in place.

Once you loosen the bolt, carefully remove the blade. Note the orientation of the blade to ensure you reattach it correctly. We recommend marking each side of the blade with either spray paint or easily removable tape before you remove it. 

Step 4: Clean the Blade

Use a dry rag or microfiber cloth to clean it. If it has a lot of dirt or grass on it, you can apply WD-40 to it, wait (per the instructions), then use a brush to clean the gunk off your blade.

Step 5: Sharpen the Blade

There are three common ways to sharpen your blade:

• Use a hand file.
• Use a power drill.
• Use a bench grinder.

Hand File

If you use a hand file, hold it at the same angle as the existing edge (usually about 45 degrees). Then push it along the edge in one direction, from the inside out. Keep doing this until the edge is about as sharp as a butter knife. Be sure to file at a consistent angle to ensure an even edge. It may not be the easiest way to sharpen your blade, but this manual method gives you greater control over the sharpening process.

Power Drill

You can use a power drill for faster results. Orient the blade so its cutting side is up and clamp it in a vise. Attach the sharpening stone to your drill, putting its plastic guide against the blade’s rear (which helps maintain the proper cutting angle). Now, carefully move the sharpening stone from the blade’s center to its tip.

Bench Grinder

Use a bench grinder if you want to sharpen it as quickly as possible. Make sure you put in earplugs and wear protective goggles if you use this tool. Carefully grind the blade’s edge against the spinning wheel, knowing that you’ll likely see sparks. It shouldn’t take more than a couple of minutes for this to work, so be sure to check its sharpness frequently.

Step 6: Check for Balance

After sharpening, ensure the blade is balanced. An unbalanced blade can cause your mower to work harder and stress its internal components to the point of needing repair. Use a blade balancer for the most accurate results. If the balance is off, remove metal from the heavier side until it is balanced.

Step 7: Clean the Blade (again)

Wipe off any metal filings with a dry rag or microfiber cloth. Spray it with a rust inhibitor for good measure.

Step 8: Reattach the Blade

Place it back on the mower in the correct orientation using the markings you put on the blade before removing it. Now, tighten the bolt securely, using a block of wood to keep the blade secure as you do so.

Wrapping Up

Bottom line: If you own a lawnmower, it’s important to keep its blade sharp. Sharpening your blade helps ensure your mower operates efficiently and your lawn continues to look great. Remember to sharpen it twice a season, gather the tools you need, and choose a way of sharpening that works best for you. 

Having a healthy, vibrant lawn takes a lot of work, but we’re here to help by providing resources like this. Keep checking back for more tips on maintaining a beautiful lawn.