How To Sharpen Lawn Mower Blades Without Removing Them? Our Guide!

Written By James
Updated July 25, 2021 by James

How To Sharpen Lawn Mower Blades Without Removing Them? Our Guide!

Can I Sharpen Lawnmower Blades Without Removing Them?

When it comes to the time to sharpen your lawnmower's blades, you might be wondering whether or not you can sharpen them without having to remove them, this can save you time from having to detach and reattach them.

It is very possible to sharpen your mowers blades without removing them, you simply need to just secure the blade and use a flat file, however, there are some important tips and steps to follow so you can do this process properly and avoid harming yourself or the mower. 

So with that being said, we have put together a small guide below that will explain to you why it's important to keep your mowers blades sharp, how often you should sharpen them and when to replace them as well as how to sharpen them while they are attached to your mower.

Let's get into it!

Why Is It Important To Keep My Lawnmowers Blades Sharp?

First of all, before we get into the process of how to sharpen blades on your mower without removing them, let's cover why it is essential to keep your mowers blades sharp in the first place.

Not only can dull mower blades ruin your grass, but they can harm your mower too, we have gone into some further detail below.

  • It puts your mower under strain - Using your mower with blunt blades can put your machine under strain and affect its other components. A dull blade can be more susceptible to grass blades wrapping themselves around the mower before being cut, causing strain and weakening the mower.
  • Discolouration on the lawn - If you continue to mow your lawn without sharpening your blades then you will be tearing the grass, not cutting it. This can cause discolouration on your garden in yellow or brown patches as the grass blades will have a loss of moisture due to the torn ends.
  • It doesn't look good - In comparison to mowing your lawn with sharp blades, your lawn will not look as aesthetically pleasing and have a less 'professional' look to it's cut.
  • Can put your lawn at risk of diseases - Fungal diseases could potentially occur on your lawn as the blunt mower will end up wounding your lawn leaving it more vulnerable to diseases getting in.
  • It can use more of your time - With a blunt blade, you will spend more time mowing to achieve the cutting height you desire and might find yourself spending more time mowing your lawn, especially on thick patches of grass.

Common Signs Your Mowers Blades Need Sharpening

Figuring out when to sharpen your mowers blades can be a little more difficult and will differ depending on the type of blades you have (for example mulching blades need sharpening more often), how often you mow your lawn and the condition of it.

To help you decide when it's the right time to sharpen your blades, we have listed out some typical signs that your blade might need sharpening.

  • The grass blades are torn not cut - Try inspecting the grass blades of your garden closely, a jagged edge to the blade will be an indication that your lawnmower's blades are tearing the grass, meaning you need to give them a sharpen.
  • Your blade is still thick and new - If your blade is still new and thick, then sharpening it is fine, as sometimes it can be hard to figure out if its time to replace the blade rather than sharpen it. Once your blade becomes a couple of years old and brittle, you should replace it and avoid sharpening it.
  • The lawn has an uneven cut - An inconsistent cut on your garden is a sure sign that the blades of your mower need to be sharpened, you may also find that you need to go over an area of your lawn more than once to achieve a consistent cutting height.

Can I Over Sharpen My Mowers Blades?

It is possible to sharpen your blades too much, consequences of doing this can mean more strain on your blade and leave it vulnerable to breaking if the blade hits a stone or some tough debris. Your blade should always be at a 40-degree angle of sharpening and never cut your hand when you touch it, otherwise, it is too sharp.

How Do I Know When To Replace My Mowers Blades?

Before we share our step by step guide on how to sharpen your mowers blades, it's a good idea to know when to replace them rather than sharpen them, as sharpening blades that need to be replaced can be dangerous and potentially risk the blade snapping during use.

We have listed out some signs you may need to completely replace your lawnmower's blades below.

  • The blade of your mower is still blunt after sharpening - If you have tried sharpening your blade and it is still blunt, or it is becoming blunt very quickly and growing brittle, you should replace your blade rather than trying to sharpen it anymore.
  • It's reached its end of life - When the age of your mowers blades reaches a couple of years, this can be a sign yours in need of a replacement rather than a sharpen, this will keep your lawnmower in the best shape possible.
  • The blade is damaged - As soon as you notice damage on your blade, whether its a couple of dents or chips, you should immediately replace it.

Step By Step Guide To Sharpening Your Lawnmowers Blades Without Removing Them

Now we have figured out when to sharpen your mowers blades and when to replace them, as well as why it's important to keep them sharp, we can get on to how to sharpen them without having to remove them.

We have put together a short step by step guide for you to follow below so as you can sharpen your lawnmower's blades safely.

Tools Needed To Sharpen Your Mowers Blades

  • Wooden block
  • Steel brush
  • Gloves
  • Flat file
  • Goggles

Step One - Seal The Gas Tank & Prepare The Mower

To begin with, you should remove the spark plug of your mower to prevent any accidental start-ups and remove the fuel tank lid (providing you have a petrol mower), then place a plastic bag over the petrol tank and put the lid back on.

Step Two - Turn The Lawnmower For Access

After you have sealed the fuel tank of your mower you can tilt it over on its side. Always make sure that the carburettor of your mower is pointing upwards to avoid oil and fuel leaking and ensure your mower is in a stable position before starting the sharpening process.

Step Three - Stabilise & Clean The Blade

Put a wooden block crosswise under your blade within your mower to keep it stable while you are sharpening, you can then use your wire brush to clean the mowing deck surrounding the blade and the blade itself. Make sure to remove any debris or grass clippings and ensure that the blade is stable enough to not make any movements for your safety.

Step Four - Sharpen The Blade

Start sharpening in the centre of your blade with a flat-file and maintain a 40-degree angle as you sharpen. Always start with the cutting edge of your blade then switch over to the other side once done. Try to make sure the blade is evenly filed on each side to prevent having an unbalanced blade.

Step Five - Lower Your Mower Back Down

Now we have successfully sharpened your lawnmower's blades we can unseal the fuel tank, tilt the mower back up and replace the spark plug.

Tips For Sharpening Your Mowers Blades

As you can see above, the process of sharpening your mowers blades without removing them is pretty simple, however, there are some important tips to remember below if you want to sharpen them safely and effectively.

  • Wear protective gear when sharpening - Always wear goggles and gloves when sharpening the blade of your mower to prevent accidental injury such as cutting yourself on the blade.
  • Empty the fuel tank before tipping your mower - To avoid fuel leaking, empty the tank first just in case to avoid any start-up problems when you tip your mower back over.
  • Always replace the blades if damaged - As soon as your blade is damaged never try to sharpen it as this could potentially cause it to snap, instead remove the blade and replace it with a new one.
  • Check the balance of your blade - You can check the balance of your blade with a blade balancer when sharpened, using a blade that is unbalanced from sharpening may cause an uneven cut on your lawn and noise from the cutting deck during mowing.
  • Sharpen your blade regularly - Keep your blades sharp on a regular schedule to avoid them getting too dull and causing issues.

Frequently Asked Questions About Sharpening Your Mowers Blades Without Removing Them

How sharp should my mowers blades be? 

Your mowers blades should never be razor-sharp and should be kept at a 40-degree cutting edge.

When should I be sharpening my mowers blades? 

On average, you should be sharpening your lawnmower's blades after every 25 hours of use, this could be around 4 times before it reaches the 100-hour replacement mark.

Why do mulching blades need sharpening more often? 

Mulching blades make much more contact with grass and debris in comparison to regular mowing blades, causing them to blunt much quicker.

Final Words

Overall, you can sharpen your mowers blades easily without removing them by using our step by step guide above, just ensure to sharpen your mowers blades after every 25 hours of use. Always remove the spark plug and tip the mower with the carburettor facing up to prevent any accidents.

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My father, and his father before him, and his father; for the past 3 generations, my family have always been into gardening. The green fingers is a gift passed down to me and I thoroughly enjoy it! I also have worked in the manufacturing department for Bosch and DeWalt so I like to think I know a thing or two about tools and such!
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