How to straighten and sharpen a lawnmower blade

sharpening a lawn mower knife

If you have a lawn, you’re probably in charge of mowing it which means you’ll have a lawn mower of some description lying around the house that you’re using to keep your lawns in tip top shape.

Like with any powered tool or machine, you’re going to need to maintain your lawnmower and fix it when blades bend or break.

In this article, we share how you can do a DIY job and straighten and sharpen your lawnmower blades, so you don’t need to pay to get it done in the shop.

While a blade replacement may be inevitable at some point down the track, sometimes a sharpen and straighten is all you need to do to keep your lawnmower firing on all cylinders.

Materials needed to straighten and sharpen a lawnmower blade include:

–   Ratchet with a long handle

–   Channel lock pliers

–   Rags

–   Ball peen hammer

–   Sledge hammer

–   File

–   Gloves

Before you start, just be aware that blades can break so if you’ve sharpened the blades and straightened them a few times eventually you will need to replace them so be super careful otherwise you might just want to go out and get a replacement if you think it’s time for a new set.

The steps for how to replace a lawnmower blade are outlined below:

how to sharpen a lawnmower blade


Step 1: Get the mower ready for you sharpen or straighten

Firstly, you will need to flip the mower on its side so that the air filter it facing upwards and that the petrol or oil doesn’t drain into the air filter.

Once you have done this, take your tools and remove the blade. When you are removing the blade, you’ll need to brace the blade against something you can use your foot or something like a piece of wood that is sturdy.

Once you have safely removed the blade using the socket and the wrench you can flip the lawnmower back over so that it sits safely on the ground.

use anvil to bend the blade back into shape

Step 2: Bending and straightening the mower blade

If you have an anvil handy, you can put the non-bend end under the anvil and then use your channel locks to slowly and gently bend the blade back, so it becomes straight again.

Failing having an anvil available, you can use something equally heavy or sturdy such as a vice or a clamp as long as you’re working on a surface that allows you to get a strong clamp when you are working to straighten the mower blade.

hammer the blade back as straight as you can get it

Step 3: Hammer the blade so it is flat

Next, you’re going to need to hammer your lawnmower blade, so it becomes quite flat.

Again, if you have an anvil, you can use this and hammer the blade on the anvil. If you don’t have an anvil, you can use a sledgehammer to get the blade flat.

use the file to sharpen the cutting edge of the blade

Step 4: Sharpen the blade

Now you need to get the blade sharp again, so it cuts your grass like a dream.

Take one of your files and hold the straightened end of the blade on your worktable and use the file to sharpen the cutting edge of your lawnmower blade.

The cutting edge of the blade is usually the cleanest part of the blade so it should be fairly easy to distinguish. When you are sharpening, you will need to put the file up to the blade, add some pressure and drag the file away from the blade, just as you would when you sharpen a knife.

Make sure all the sharpening strokes go away from the edge of the blade. Some power tools have a sharpening attachments, so if you have one of these pop it on and you’re away.

reattach the lawnmower blade

Step 5: Reattach the blade to the lawn mower

You’re getting towards the end of the job now, and you can start reattaching the lawnmower blade to the machine.

Put the lawnmower on its side again at this point, take the straightened blade with your wrench and socket and reattach the mower blade in a reverse fashion to when you took it off.

Make sure you are super careful with reattaching the lawnmower blade and make sure you have tightened the blade properly.

If you think that it’s not worth straightening and sharpening your lawnmower blade and it’s far easier to just replace the blade with a new one, there are a few easy steps to installing a new blade.

Here’s how to replace the mower blade with a new one:

–   Set the mower on its side

–   Remove the fasteners that hold the mower blade on

–   Remove the old mower blade

–   Install the new mower blade

–   Made sure the blade is the right side up

–   Ensure the blade is tightened correctly

Straightening, sharpening or even replacing your lawnmower blades isn’t difficult however you should always be very careful with safety and wear protective gloves when working with blades.

As well as this, if you are going to DIY your mower blade maintenance, make sure you are careful with touching the blades, and you are also aware of the petrol and oil in the machine when you are tipping it to one side and working on the machine.

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