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Have you noticed that your lawn mower isn’t as efficient as it used to be?

Maybe it’s not cutting grass as well, or it’s ripping out chunks instead of slicing through them. Or perhaps you’ve accidentally hit something and caused damage to your mower blade.

Now, you could opt to sharpen your lawn mower blade, but that’s not always the best solution. At some point, the blade of your lawn mower will be dulled beyond repair, or maybe cracks or holes will occur.

To replace a lawn mower blade, you’ll first need to shut off the mower and/or disconnect the spark plug. Remove the main bolt and each blade bolt. Then take your replacement mower blade kit and replace the old blades with new blades.

When you’re mowing your own lawn, you’ll need to keep your blades sharp and intact. Learn how to change lawn mower blades to maintain your mower properly.


Why Change Blades on Lawn Mowers?

Simply put – to cut grass properly and efficiently. Dull or damaged blades won’t trim grass well (if they can cut at all).

They might also cause damage to your mower by straining the engine, using up more fuel, and possibly overheating the equipment.

Even the best lawn mowers will have their blades wear down over time. So ensure you not only sharpen your blades, but change them regularly too!


Lawn mower in the garden


Should I Sharpen or Replace Lawn Mower Blades?

Check the condition of your blade to determine whether it needs to be sharpened or changed. Tilt your mower back flat or lower the mower deck.

Ensure there’s no petrol or oil flowing towards the blades, or that could cause a bigger problem!

Inspect the blades for any:

  • Cracks
  • Bends or warping
  • Holes
  • Excessive thinness

If any of these are the case, then you’ll need a new blade. Excessive vibration, running over obstacles, and general wear and tear can all cause damage.

Otherwise, if the metal is still thick and there’s no visible damage, all you’ll need to do is sharpen them.

Most lawn mower blades are easy enough to fix so long as you’re careful about safety. Changing the old blade yourself will also help you save money.

But if you’re apprehensive about switching out your blade, take your equipment to your local mower shop.

(Pro Tip: It’s a good idea to get your mower maintained once a year, just so a professional can inspect the whole machine and make sure it’s in good nick!)


How to Change a Lawn Mower Blade

Always start by turning off your mower and disconnecting your spark plug wire. Wear protective gloves while working – blades are sharp!

You can also opt to empty the petrol tank, especially for ride-on mowers.


Things to check before changing blades

Check your manufacturer’s specs if there are specific instructions for changing mower blades.

Most blades follow the same instructions, but you may need to check the specs for hardware or special styles. 

Before you begin, look at the:

  • Style of blade
  • Size of bolts
  • Thread of bolts

Note that the thread of the bolt will determine the direction in which you turn it.

Traditional bolts turn left to loosen, right to tighten – but reverse-thread bolts go the opposite way. Check the kind of thread first!


man changing lawn mower blades


Changing push mower blades

It’s pretty straightforward to change push mower blades. Once you’ve prepped your garden tool, get started.

  1. Remove the retaining bolt. You can use any old socket wrench that’s the right size. Be mindful that the blade doesn’t drop while you do this!
  2. Take out the old blade. It should come right off once the retaining bolt has been unscrewed.
  3. Replace with a new blade. Check that it’s in the correct position – there should be a guide or instructions to follow.
  4. Re-tighten the retaining bolt. Screw it back on, ensuring the blade doesn’t move or wobble.
  5. Reset your mower. Stand it back up and replace any fuel you syphoned out. If you need to use it immediately, reattach the spark plug or restart the engine. Let it run for a bit to ensure the blade is spinning correctly – then you’re good to go!


Changing ride-on mower blades

ride on mower

For a ride-on mower, you’ll need a different way to access the blade mounting hardware in order to change the blades.

  1. Drop the mower deck. Set it so that it’s at its lowest possible point.
  2. Take out the deck. You’ll need to disengage the belts and release the belt.
  3. Unscrew all bolts. Take a correctly-sized wrench and loosen the bolts and brackets. Lay them out in an organised manner so you can replace them all when you’re done.
  4. Remove the mower deck. Once all the connections are unscrewed and the blade cable has been disengaged, the mower deck should slide out.
  5. Change the blades as you would a push mower. Unscrew the retaining bolts, take out the old blade, and put in a new one.
  6. Reconnect the mower deck. Re-tighten the bolts and brackets to reconnect the deck to the mower. Set the deck back to the appropriate setting and you’re done!


What Happens If You Put Lawn Mower Blades on Upside-Down?

Sometimes, if we’re not paying too much attention or if we’re rushing, we may insert the lawn mower blades upside-down. It’s always good to double-check, since this can create some problems.

Upside-down lawn mower blades can cause your mower to cut incorrectly since it’ll be slicing with the dull side. This can lead to damage to your mower itself.

The biggest sign you’ve installed the mower blades upside-down is an uneven, rough cut on your lawn after you’ve changed your blades.

This is because the mower isn’t blowing the grass correctly, and the dull side is ripping the grass instead of cutting it.

How to know if you’re installing lawn mower blades correctly? New blades will have a sticker or etching that reads “This Side Down” or “This Side Towards Grass.” Simply follow those instructions.

Alternatively, you can look for the cutting edge (sharpened) which should point away from the mower deck. The dull trailing edge (which has a bend) will point towards the deck.


Maintaining a Lawn Mower

Take it from the lawn experts – knowing how to change lawn mower blades is an essential skill for lawn owners.

Your mower’s blades play a key role in cutting grass efficiently and maintaining the lawn’s appearance.

Otherwise, you’ll have a garden tool that cuts unevenly – or even rips out chunks of your lawn and ruins your hard work!

About Author

Jamie Donovan

Jamie is an Australian horticulturalist and landscape designer. He enjoys writing about landscape architecture, garden design and lifestyle topics.


About Author

Jamie Donovan

Jamie is an Australian horticulturalist and landscape designer. He enjoys writing about landscape architecture, garden design and lifestyle topics.