Any keen gardener will know the importance of keeping your lawn mower blades nice and sharp, as well as what happens if you don’t. But not everyone knows the best way to go about sharpening mower blades. Is it possible without removing them first?
Whether you have a push mower of some kind or a riding lawn mower, sharp blades are the key to grass-maintaining success. Sharp blades will help to ensure all blades are sliced cleanly and evenly rather than being ripped haphazardly, and will also help to keep your grass and soil healthy.
For more information on how sharp blades are one of the cornerstones of thriving lawns, and how dull blades can damage grass both aesthetically and health-wise, check out this post.
Because push mowers and riding mowers are so different in shape and assembly, it makes sense to tackle blade sharpening for each one individually. As push mowers are more commonly used by residential gardeners and those with small plots of land, that’s where we’ll start!
Before we get there though, let’s go over some basic but important safety requirements.
Whether they’re at peak sharpness or not, lawn mower blades of any size and type can be dangerous. To minimise the risk of accidents and injuries taking place, it is vital that you have all the right safety equipment prior to beginning.
For your own personal safety, you should consider the following:
You also need to think about how to make the lawn mower as safe as possible while you’re working with it, but we’ll look at this in more detail for each different example.
Is it possible to sharpen your push mower’s blades without removing them from the mower? In most cases, the answer is yes. Because most lawn mowers are fairly easy to manoeuvre, lift, and turn, it doesn’t matter too much about what type of push mower you have, be it electric, petrol, or traditional manual.
No matter the type of lawn mower you’re working with, there are several bits of equipment you’ll need for the sharpening process:
Once you’ve got these things, you can begin.
Start by ensuring your lawn mower is not plugged in (if it’s electric) or remove the spark plug (if it’s petrol). Basically, whatever you need to do to ensure the mower will not start up while you’re working, do that! The last thing you want is to lose a finger. This is the most important safety step in the whole process.
Next, you want to carefully tip the lawn mower onto its side. Be cautious when you do this as even though most lawn mowers are easily moved by one person, they’re still heavy and can damage your back if approached too casually.
If you’ve got a petrol mower, ensure the fuel tank and carburettor are on the uppermost side.
Wedge the wooden block underneath your mower to keep it stable and make sure it doesn’t wobble even if you apply some pressure. Sharpening blades is risky business so it’s best to ensure the mower isn’t going to fall on top of you while your hand is inside it.
Take a second wooden block and use it to secure the blades by wedging it under the blade. Use your putty knife or scraper to remove any debris stuck to the blades, using some water to rinse away any remnants before you begin sharpening.
At this point you can also use the steel wool or wire brush to scrap away any rust or other stubborn mess that will interfere with the sharpening process.
Once the blades are clean and clear, it’s time to start sharpening. Because you want to end up with as close to a 45-degree angle at the edge of your blade as possible, you’re going to move your grinder or file in one direction only as opposed to going back and forth.
Whichever of the two tools you use, you’re going to start at the centre of the blade and work outwards towards the edge, maintaining enough pressure throughout to ensure you’re creating an angle. This angle will be what results in sharpness.
Most lawn mowers have two blades made from the same piece of metal – in other words, each end of the metal bar is a blade. You’ll need to repeat the sharpening process for both blades. Instead of trying to reach over to the furthest one away from you, unwedge the wooden block keeping the blades stable and turn the blades so the next one is in front of you, then restabilise it with the block.
When both blades are equally sharp (try to get them as similar as possible in order to keep the blades balanced), you can remove the wooden block and return the mower to its upright position, ready for it to be used again.
Because riding mowers are so much bigger and heavier than an electric or petrol lawn mower, the process for sharpening their blades without removing the blades is quite different and far less ideal.
In theory, you should be able to follow similar steps to those detailed above however, because riding mowers are so large and heavy, you can’t just tip it onto its side to see get access to the blades. You’d need to lift the riding mower with a jack or similar system in order to get underneath it.
Before even doing this, you need to make sure the ignition is off, all switches and levers are off, and that your parking brake is engaged. You can also wedge the tyres with bricks to make double sure that the mower isn’t going to roll or move while you’re working. You also need to remember to remove the spark plug.
Once you’ve done this and have lifted the mower up, you can then set about cleaning and sharpening the blades. While this is possible to do without removing the blades, it will be very awkward and difficult, and will likely result in subpar results with unbalanced blades.
For this reason, it really isn’t practical, and it would be much simpler, easier, and quicker to sharpen the blades after removing them. It would also be safer for you and give you a better, more even result. Long story short, you’re far better off removing the blades of your riding mower.
The first thing you’ll need to do is make sure everything is off and unplugged as mentioned above. Once you’ve lifted your riding mower and you’re sure it isn’t going anywhere, you can use a clamp or a block of wood to wedge the blades in place to make it easier to remove them.
The blades are held onto the spindle by a nut, which once removed, will allow the blades to just slip off. You can remove this nut using an appropriately sized socket wrench. If you try to turn the nut without securing the blades first, the blades will naturally try to turn along with the nut.
By securing the blades in place with your wooden block or clamp, you will get more leverage on the nut and be able to turn it more easily to release it. Once you remove the nut, the blades should fall off the spindle easily.
With the blades removed, you can then get on with sharpening them, which you can do with the same tools and method as the push mower, using a file or grinder to create as close to a 45-degree angle at the edge of the blades as possible.
To do this, you’ll need to start in the centre of the blades and work outwards towards the edge as described above, lifting the grinder or file after each sweep and thus avoiding a back-and-forth motion.
Removing your riding mower blades will allow you a much better visual so that you’ll be able to balance the blades much more accurately and easily. To try and do this well with the blades still attached to the mower deck will almost certainly result in unbalanced blades and an uneven finish.
Once the blades are sufficiently sharpened, you can reattach them to the deck by replacing and tightening the nut. Then all that’s left to do is lower your mower back to the ground, plug everything back in and you’re good to go!
We’ve now seen how it is possible to sharpen a push lawn mower’s blades without removing them from the mower first. In the case of the different types of push mowers, it’s actually fairly simple and shouldn’t take you too long.
With that said, you’re still probably likely to get better, more balanced results if you take the blades off the mower before sharpening them. This allows you to see all angles of the blade better as well as make sure that each side is equal. So, although it might be slightly more effort, removing the blades is still probably the better way to go for optimal results.
In the case of riding mowers, keeping the blades attached to the deck whilst sharpening them is difficult, awkward, and even dangerous so without a doubt, removing them to sharpen them is the best way forward. It will be quicker, easier, and will give a much better end product.
It’s always better to take a couple of extra steps and do thing’s properly the first time round than to have to correct mistakes at a later stage. It’s also important to know when you’ve met your match and when replacement is a better option than sharpening.