How to Sharpen Lawn Mower Blades

Keeping your lawn in top shape calls for a lot of overtime and hard work, but knowing how to sharpen your lawn mower blades is half the battle. Learning how to sharpen mower blades is often an overlooked job, that’s why keeping your blades sharp should be an essential part of your lawn mower maintenance routine. If you’re looking for a lawn to be proud of, mowing the garden with a blunt blade is a common mistake that can damage and ‘scalp’ your grass. This can often lead to lawns looking unfinished and vulnerable to disease. Forgetting to sharpen your lawn mower blades can also push your mower to work harder, leading to more frequent repairs and replacements in the long-term. It can be overwhelming to pull apart your lawn mower and sharpen its blades, that’s why FarmCare Mullumbimby is here to help guide you on how to safely sharpen your lawn mower blades and get your edge back.

When Should I Sharpen my Lawn Mower Blades?

It’s easy to lock your lawn mower in the shed after you’ve finished the job, but it’s important to regularly and proactively inspect your mower to check if it needs sharpening as part of your lawn mower maintenance. 



Regular Checks

It’s best to check your blades regularly before you start seeing signs of lawn damage or mower wear and tear. Checking your blades after big lawn mowing jobs can help prevent any unwanted damage. 



Replace a Damaged Blade

Cracked or chipped blades cannot be sharpened or filed down. Damaged blades need to be replaced entirely.



How Frequently Should I Sharpen my Lawn Mower Blades?

A general rule of thumb is to sharpen lawn mower blades typically after 20-25 hours of use to stay in good shape. However, depending on your mowing frequency, type of terrain or grass type, sandy or rocky areas can dull the blades faster and may require you to sharpen your mower blades. 



Get the Edge: How to Sharpen my Lawn Mower Blades

1. Safety First

It’s no brainer to prioritise your safety first and to make sure that your lawn mower is powered off, before starting any sort of lawn equipment maintenance. This will ensure that you do not accidentally turn on the mower while adjusting the blades. For electric mowers, detach the cable from the power source and wind it around the mower to prevent people from reconnecting the wires while you work. If you have a cordless mower, remove the battery, and for petrol-operated mowers, disconnect the spark plug.

2. Position the Mower

To access the underside of the mower, you need to start with tipping the mower on its side. While electric mowers can be easily turned upside down, air filters on petrol mowers must always be on top, otherwise there is a risk of engine oil draining onto the filter and damaging the mower. Alternatively, you can drain the gas tank to avoid any fuel spills before commencing any work. You can tilt a petrol mower to a maximum angle of 45°, or alternatively place it on top of two chairs so you can get underneath it.

3. Remove the Blade

Before removing the blade, it’s essential to remember its orientation in the mower to ensure the blade is facing the right side up when re-assembling. It’s best to mark the blade on the upward-facing side to remind yourself what way to replace it later. Find the nut that holds the lawn mower blades to the drive shaft, and use a wrench or socket tool to loosen the nut until the blade releases. Using one hand, hold the blade in place, and use the other to remove the bolt. If it is difficult to remove the bolt single-handedly, you can wedge a wooden block between the blade and the lawn mower to keep it in place, and then loosen the bolt. 

4. Clean the Blade

Before sharpening your mower blades, you should clean any dirt or grass clippings with a soft, microfibre cloth. If you see any cracks or chips on the blades, this cannot be filed down and must be replaced.

5. Secure the Blade

To safely sharpen your blades, secure the blade in a vice that allows the cutting edges to be easily filed.

6. Sharpen the Lawn Mower Blades

There are several ways on how to sharpen your lawn mower blades:

Sharpening File

Taking a metal sharpening file, use angled strokes in one direction to follow and sharpen the direction of the curve. Applying enough pressure to the edge, maintain a sharpening angle of 30° and repeat the filing process until the blade edge is smooth. Sharpening with metal files will give you more control and precision. Ensure that your blade is only as sharp as a butter knife when you are finished. Make sure to repeat this process on the other side!

Blade Sharpener

If you’re feeling confident, you can use a drill powered blade sharpener that inserts onto a drill. Place the flat part of the sharpener on the back edge of the blade, and the curved edge of the sharpener on the curved edge of the blade. Run this sharpener over the blade a few times until the blade sharpness is equivalent to that of a butter knife. Be careful not to overheat the blade when using a powered sharpener, as this may damage the blade. 



7. Check the Blade Balance

You must check that the blade is balanced, to ensure that the weight of the blades is equal all-round. During the process of sharpening the blade, it can be challenging to tell how much metal you have filed off, making the blades become unbalanced. Leaving the blades unbalanced can cause it to tilt and potentially damage your lawn mower. To check your blade’s balance, place the centre hole of the blade onto a balancer and let go. A balanced blade will stay level, whereas an unbalanced one will dip towards the heavier side. If unbalanced, sharpen the heavier side of the blade slightly until it hangs level. If the blade leans to one side, you should remove weight from the heavier side, repeat steps 6 and 7 until it is perfectly balanced.

8. Reassemble the Blade

Using the markings from step three, ensure the blades are reinstalled in their original orientation. Facing the right side up, tighten the nuts or bolts by hand until it is secured tightly, and that everything is assembled properly.



Still Unsure? FarmCare is here to help!

We understand that pulling apart your mower and sharpening your blades can be an extra hurdle. If you’re looking to sharpen your lawn mower blades without the pressure or safety concerns, let us take the stress out of the job. At FarmCare Mullumbimby, our skilled technicians offer reliable servicing and repairs for a wide range of gardening, landscaping and agricultural gear. Get in touch with us today, we’ll have your lawn mower back up and running in no time!