How to sharpen lawn mower blades without removing Them?

Photo of a lawn mower tipped to the side and its owner sharpening the blades. How to sharpen lawn mower blades without removing them?

One of the most critical parts of lawnmower maintenance is getting and keeping the blades sharp. When we first buy a new mower, we often love how crisp and clean it cuts the grass. Fast forward a few seasons, and if you haven’t been regularly sharpening the blades, your lawn will reflect that with a scraggy cut.

It’s not even that difficult to sharpen a blade, and it doesn’t take very long to do. The inconvenience of getting access to the blade and removing it is the most frustrating for most. Below we’ll look at ways how to sharpen lawn mower blades without removing them.

Can you sharpen mower blades without removing them?

Yes, it is possible to sharpen a mower blade while still attached to the mower deck. It may not be as convenient to sharpen a blade when it’s connected to the mower, but it can be done.

The knack is positioning the mower deck so that it gives you access to the blade so you can get sharpening at it. Obviously, it will be easier to get access to a small push lawnmower than to a large riding lawnmower or a zero-turn mower. Still, the tools we will be using only require limited access for them to sharpen the blade.

How do I know if my lawn mower blades are blunt?

It’s pretty easy to see that your mower blades are blunt. After you have cut the grass, bend down and look at how the tops of each individual blade were cut.

If the blade is dull, it won’t cut the grass cleanly – as though it had been cut with a pair of scissors. Instead, the grass will have a torn look to it – this is because the blade is not sharp enough to cut the top of the grass blades, so it rips through the grass instead.

Although I said to bend down and check the top of the blades of grass, it will be quite apparent when you look at the whole lawn – it will look dull and ragged instead of crisp and clean. 

Best tools to sharpen lawn mower blades

There are not many tools you can use to sharpen mower blades when they’re still attached to the mower because access is so limited. I will run through the list and explain how each one works and how well it performs at sharpening the blades.

Sandpaper

It has been said that you can use sandpaper to sharpen mower blades, but I would argue against it. Extreme caution is needed if you decide to sharpen your mower blades with sandpaper because of how the sharpening takes place.

To sharpen the blade, you’ll need to rub the sandpaper along the blade edge, backward and forwards, hundreds of times. This abrasive action removes small amounts of steel from the blade and will brighten and sharpen the blade edge.

One problem with using sandpaper is that it can’t be any old sandpaper – it needs to be emery paper specially designed for rubbing down steel. Regular wood sanding sandpaper will disintegrate quickly and not wear down the steel at all.

The other problem with using sandpaper is that it takes so long to sharpen a blade. Sharpening a mower blade with sandpaper will take you the longest of all the methods.

The final problem with using sandpaper is the most important one – Safety. It is so dangerous to use sandpaper to sharpen a mower blade that it surprises me anyone does it. Just imagine the only thing separating the skin on your fingertips and a sharp steel blade is a piece of sandpaper.

To sharpen the blade, you will vigorously rub the sandpaper using your fingers along the blade. One error, and you will slice your fingers or hand in bits.

A flat file

Using a hand flat file is a much better way to sharpen a mower blade than using sandpaper.

Rub the file backward and forwards at the desired angle until the blade is nice and sharp. It may not be easy to sharpen the blade’s top edge as it is still relatively close to the mower deck – but it can be done.

It’s good if the blade hasn’t totally lost its edge, as using a file is still quite labor-intensive compared to using an angle grinder or a sharpening stone.

A grinder

An angle grinder is great at sharpening steel blades, although access may prove to be the biggest hurdle. The grinder is the most cumbersome of all the tools to get in around the mower blades with. It will also take the most metal off the blade the fastest.

Safety is important when using the grinder because One wrong move and it could slip out of your hands and cause an injury. Plus, it sharpens blades in no time flat. I’m talking razor-sharp. 

Suppose you forget that you have already sharpened a blade. You could put your hand on it accidentally with terrible consequences. So make sure to handle it with care!

Sharpening stone

The sharpening stone on an electric drill is probably the best tool to use if your blades are in quite good condition and just need a quick sharpening.

The sharpening stone has an angled slot so you can sharpen the blade’s top edge while keeping the power drill on the bottom side of the blade. Pulling downwards and moving the stone along the length of the blade with the drill sharpens the blade’s top edge.

To sharpen the bottom edge of the blade, you simply push upwards with the drill to engage the bottom face of the stone with the bottom edge of the blade.

The sharpening stone is excellent for access and safety. It won’t take a lot of steel off the blade, but it will be good enough to sharpen it from being dull.

Photo of lawn mower blades being sharpened with a sharpening stone.

Safety precautions before sharpening lawn mower blades

Remember to wear the appropriate PPE before starting to sharpen the blades. Safety gloves are a must to protect your hands, safety glasses and ear protection when using power tools, and safety boots are recommended if you are working on heavy mowers that need to be jacked up.

Sharpening lawn mower blades without removing step by step 

In the above section, I wrote about how to sharpen a mower blade using different sharpening tools. In this section, I will discuss how to access the various types of lawnmower cutting decks and their blades.

Push lawn mower blades

As push mowers are quite small and light, they can be lifted onto their sides to allow you access to the blades. Remember to drain the fuel tank or ensure it is nearly empty before tipping it over on its side.

Before tipping it over, check which side the engine oil filler is on. This side needs to be uppermost. Otherwise, all the oil will leak out.

If the blades are a little blunt, either use a drill with a sharpening stone or a hand file. If they are very badly battered, use an angle grinder with caution – watch where the sparks are going and alert others in the immediate area to stay back.

Riding lawn mower blades

Riding lawnmowers are a little different as they are a lot bigger. To access underneath your mower, you have two options: create ramps for the front wheels to drive up onto or lift the front of the mower using a jack and secure it with blocks or stands.

The other point to check is that the wheels are trigged so the mower cannot move from its raised position.

Ensure the blades are fixed in position before you begin to sharpen them. This can be done by jamming a piece of wood across one end of the blade to keep it steady while you sharpen it.

The same sharpening advice follows for these blades as the push mower above. Use a drill or hand file when the blades are only slightly dulled, and use an angle grinder when the blades are very blunt or battered-looking.

Zero-turn mower blades

As zero-turn mowers have their blades and mower deck sitting out in front, you will need to assess whether you can raise the mower deck by jacking it up or driving the front wheels up on ramps.

You might damage the linkages on some zero-turn mowers if you were to jack them up by the cutting deck, as the full weight of the mower is being held by the linkages.

It is probably a much better idea to drive the front wheels up on ramps and then stop block the wheels so the mower cannot move. The same advice applies to sharpening zero-turn blades as the other blades. Flat file or sharpening stone for light sharpening and an angle grinder for extreme sharpening

How many times can you sharpen your mower blades?

Depending on how much material you remove from the blade, a mower blade can be sharpened many times. I would say it could be sharpened lightly, maybe 30 to 40 times.

You will know when the blade is worn out and needs to be replaced, as it should not be more than ½” narrower than the blade originally was when it was new. Excessive sharpening weakens the structure of the blade, which can cause it to buckle and bend.

What is the easiest way to sharpen lawn mower blades?

Using an angle grinder is the fastest way to sharpen a blade, but using the drill with the stone is the easiest way.

The grinder is harsh and dangerous, but the drill is safe and has low impact. The file and the sandpaper are exhausting to use as they require a lot of physical labor.

We have discussed that we can sharpen lawn mower blades without removing them from the cutting deck. We can use sandpaper, an angle grinder, a hand file, or a sharpening stone on a power drill.

The next hurdle we face is getting access to the blade in the cutting deck. Small mowers have easy access, riding lawnmowers should be jacked from the front, and zero-turn mowers may require front-wheel ramps.

As I mentioned before, I would strongly advise against using sandpaper as the risk of injury is so high.

Jerry Olguin

Jerry is a lawn mower afficionado with over 10 years of experience in the industry. He is knowledgeable about a wide range of mower brands and models and is always eager to share his insights with others. When he's not busy maintaining his own lawn, Jerry can often be found tinkering with mowers or helping friends and neighbors with their lawn care needs.