How to Sharpen Mulching Blades Safely in 8 Easy Steps

A gardener is only as good as his tools. This is a very valid statement for me when I discover my lawn mower isn't cutting as well as it used to. If you mow your lawn without sharp blades, you might find that 2-3 days afterward your lawn will have a brown cast to it, which won't look good!


This article will show you exactly how to sharpen mulching blades, from start to finish, and in the safest way possible.

What will you need to get started? Well, let's find out!

Sharpen Mulching Blades

What You Will Need to Follow This Tutorial

1. A Pair of Welding Gloves

You'll need these gloves to protect your hands whilst holding the blade. You'll also need them if you're using a grinder.

2. A Clamp

This will hold the blade in place whilst you unscrew the nuts. This means you don't have to hold the blade with your hands and is a lot safer.

Many people use a 2x4 piece of wood to hold the blade in place but if it's not wedged in correctly, the blade can move. I'd only recommend using a 2x4 if the lawnmower is resting on the ground, rather than a table.

3. A Wrench

The nut(s) holding the blade in place will be very tightly screwed on. Using a wrench will give you enough leverage to loosen the nut.


Make sure the wrench will fit the nut exactly otherwise you may round it off and make it hard to unscrew.

4. A Socket (Optional)

Once you've loosened the nuts, a socket can make removing the nut very easy. There's no other reason to use a Socket over a Wrench though.

5. An Old Rag

Cleaning the grass from the bottom of your lawn mower is just as important as sharpening the blades and can extend the longevity of your lawn mower.

6. Metal File

You can sharpen the whole blade by just using a metal file.

Another way to sharpen the blade would be to use a Grinder. This will do most of the work for you but it's more dangerous, obviously.

7. Eye Goggles (Optional)

If you do decide to use a grinder, please use eye goggles to ensure you don't get any metal fragments in your eyes!

Step by Step Instructions

#1 Tilt the Lawnmower

Tilt the Lawnmower

Tilting your lawn mower the wrong way can damage it for a number of reasons. Gas or oil can leak into it and might mean you'll have to replace the whole thing.

The "right" way to tilt your lawn mower depends on whether it has its petrol and oil separated. If so, then tilt the mower so that the spark plug is pointing upwards.

If your lawn mower mixes the oil and petrol, make sure you turn off the fuel tap first.

#2 Remove the Spark Plug

Safety should always be paramount in your mind when you're removing or reattaching mulching blades to your lawn mower.

You don't want your lawn mower to accidentally start as it might cost you a couple of fingers!

When you remove the spark plug, make sure that there's no way it can accidentally connect with the starter. The best way to do this is to push it up and away into a crevice in your lawn mower.

#3 Tighten the Clamp

When you're unscrewing the nuts you'll want to make sure that the blade isn't going to be moving. It can be dangerous for you and it might also damage the blade.

With the blade in a vertical position, place the clamp on the left side if you're right handed, and vice versa if you're left handed. The clamp should be touching the blade and should be very tight.

Alternatively, you can use a 2x4 piece of wood to jam the blade in place. Just make sure that it's stable and won't slip. This video shows how to perform this technique.

#4 Unscrew the Nuts

Now that everything is secure, you'll want to begin removing the nuts with the wrench. Make sure you have your welding gloves on to stop yourself getting cuts on your hands.

Once you've loosened the nuts, you can finish the job with a socket so it's faster. You might find it easier to remove your gloves at this point as using welding gloves with a socket can turn you into a butter-fingers!

You can see how this is done via this instructional video.


Hold the wrench almost parallel to the blade leaving up to a 45° angle between them. This will let you squeeze your hand together, making it easier to loosen the nuts.

#5 Remove the Blade

Now that the nuts are off, you can remove the blade. Handle it with care to make sure it's not a danger to yourself or anybody else, and put the blade bell support in a safe place as you'll need it later for when you reattach the blade.

Make sure you secure it in a vice or clamp right away and don't leave it lying around as that's how injuries can happen.

#6 Clean the Lawnmower

Clean the Lawnmower

If there's grass and debris stuck to the bottom of your lawn mower then now is the best time to clean it. You should be able to get rid of everything with an old rag and some water. Dampening the rag with hot water can help to get rid of any pieces that are stuck.


When you cut the lawn, check the grass. If there's a nice clean cut then there's no need to sharpen the blades. If it's ragged on the edge, that's a sign your blades aren't cutting well.

#7 Secure the Blade with the Vice/Clamp

The main goal here is to keep the blade nice and steady while leaving the blade open so you can work on it at any angle you need to.

Here is a video of how to easily clamp your blade to a table. If you skip to 6:00 the important information is there.

You'll need to be able to work on both sides of the cutting edge of the blade so bear that in mind when clamping.

If you need to readjust the blade and you're using a grinder, make sure it's turned off first.

#8 Sharpen the Blade

If you're using a grinder, this video will give you an excellent benchmark to work from. Using your protective eye wear will stop any metal fragments from potentially blinding you.

If the edge is a little too sharp when you've finished, you can blunt the edge of the blade with a file by running it over the blade, using the flat edge of your metal file. If you see any metal being bent over, just file it off.


Once you've finished sharpening the blade, hang it on a nail to see if the blade is balanced. If one side is heavier, work on it some more to get a balance. This will reduce the chances of damaging your lawn mower.


Over time you might just decide to replace your mulching blade with a new one. This article explains how to pick out the perfect blade for your circumstances.

If you keep it sharp before you mow, you'll get the most out of it. It will last longer and, in turn, save you money so you're not replacing anything sooner than you need to.

I hope you enjoyed the article and I'd love to hear any comments you'd like to make. If you found the article informative you could share it with your friends, too!

About the Author Laura Bennett

Hello, I’m Laura Bennett. I love nature especially when it comes to flowers and different kinds of plants. I started a very small garden behind my house and I named it Humid Garden. So, I created this blog to provide aspiring and inspiring thoughts about gardening for gardeners and anyone who has the intention of keeping a garden.

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