How to Sharpen Lawn Mower Blades without Removing

Lawnmower maintenance is a lot of work. Besides the daily routines of checking fuel, oil, and tires, you also have hourly checks like air filters, batteries, spark plugs, mower blades, and so much more.

That’s why we love lawnmower hacks that make maintenance fast. One question we often get is how to sharpen lawn mower blades without removing them from the mower.

But is that even possible? This article will answer that question as well as how often your blades need sharpening, why and the best way to sharpen lawnmower blades.

How to Sharpen Lawn Mower Blades without Removing

Seal the tank
Cut off the power supply
Tilt the lawn mower
Clean the mower deck
Sharpen the blade
Return the mower to position

Can You Sharpen Lawn Mower Blades Without Removing Them?

Yes, you can sharpen lawn mower blades while still on the mower. The best way to sharpen a lawn mower blade is to take it off and hold it in a vise.

However, some people can’t remove the mower blade because of rust or don’t have the tools to remove it, while others are in a hurry.

Whatever the case is, there is a way to safely sharpen lawn mower blades without removing them.

When Should I Sharpen My Lawn Mower Blades?

The simple answer is that you need to sharpen lawn mower blades as soon as they feel dull. The more scientific answer is that you should sharpen lawn mower blades every 25 hours.

For the typical residential user, you only need to sharpen your blades once a season.

For commercial mowers, this equates to roughly once a week or once every month, depending on how active you are.

However, if you work on lawns with many stones, they will chip at your blade faster, so you may have to sharpen the mower blade after every session.

Is Sharpening Lawn Mower Blades Beneficial?

No matter how dull your mower blades get, chances are high that they will still mow the lawn.

So, what’s the point of sharpening your lawn mower blade or replacing it if that’s the case? Is it just a way to sell more products?

There are several reasons why you should sharpen a dull mower blade, but we’ll only discuss the three most important ones.

It gives a cleaner, healthier cut

Cutting a lawn with dull blades is like ripping a chunk of steak instead of cutting it with a knife. They both get the job done, but one is cleaner, neater, and less likely to get meat juice in your eye.

In the case of grass, a clean cut is more visually appealing. However, there is also a biological reason. A dull mower blade shreds the grass instead of cutting.

This jagged edge heals slower and requires more nutrients. Before it heals, it will turn brown after a couple of days, and your lawn will look nasty.

In this state of recovery, the grass is vulnerable to diseases because the nutrients are too busy working overtime instead of protecting the healthy grass from external threats.

Unless you want a brown, sickly lawn, it’s best to use only sharp lawnmower blades.

You get more even cuts

For professional landscapers, the frustration of surveying an uneven field left by a lawnmower is all too familiar. The perplexing question often arises: Why is my mower leaving a strip of grass?

Even for homeowners using lawnmowers for their residential lawns, this issue might not bother them greatly until the time comes for family gatherings or visits from relatives.

The reliability of lawnmower blades hinges on their sharpness. Dull blades don’t simply cut the grass; they end up yanking at it. As a result, achieving a consistent and even cut becomes nearly impossible.

In addition to the unsightly jagged edges of the grass, certain areas end up visibly taller than others. This disparity in height further accentuates the uneven appearance of the lawn.

It produces less drag on your engine

When working with a dull blade, there is more drag because it is not slicing through the air as it should.

This forces the blades to work extra hard, putting a strain on the spindle, the pulley system, and the engine.

It’s almost like cutting an apple with the back of a knife; it will still get the job done, but it will require more effort.

Eventually, this excess strain will wear down or age your engine because it constantly works overtime. If you want to prolong the life of your engine, keep your blades sharp.

When Should I Replace Lawnmower Blades?

There will come a time when sharpening lawn mower blades won’t work. The average lawnmower blade lasts for about 200 hours.

This means the typical blade must be replaced every four to five seasons. Gator blades can last twice as long.

That said, you shouldn’t wait until then if you notice major deformities with your blade. Deep gouges and cracks are clear signs to replace lawnmower blades.

Also, if you notice that the bevel has almost completely worn off, you should take that as a hint to get new blades.

How Sharp Should The Blades Be?

So, how sharp should mower blades be? You would assume that the sharper the blade, the better it is, but this is not the case when it comes to lawnmowers.

Thanks to the incredible speed at which they spin, lawn mower blades don’t need to be razor sharp or razor thin to cut. If your lawn mower blade is not spinning, check out our detailed article to find out the reasons why.

You should be able to gently touch the edge of sharp blades without them cutting your finger. That is why even brand-new lawn mower blades seem dull but will cut grass effectively.

When sharpening the mower blade, you only need to take off the darkish tinge on the bevel until the metal begins to shine. Also, ensure you maintain the same angle of the blade.

If you try to make the edge razor-sharp, two things will happen. First, the edge will become too brittle and won’t last after a few hours of cutting.

Second, the blade will become unbalanced, and you will alter the slope of the bevel. That is why you should only sharpen mower blades as the manual directs.

Step-by-Step Guide: How to Sharpen Lawn Mower Blades Without Removing Them

The easiest, best, and recommended way to sharpen a lawn mower blade is by first taking it off and putting it in a vise.

However, if that isn’t an option, here is how to sharpen lawn mower blades without removing them.

Lawn Mower Blade Sharpening Safety Tips

Sharpening a lawn mower blade can be dangerous even when precautions are taken, so you must be mindful of a few things.

The first thing is always to wear protective equipment. Ensure you’re wearing cut-resistant gloves and safety goggles.

The latter is very important if using a rotary tool, as these can send metal shards flying toward your face.

You should also consider using ear muffs if using an angle grinder. Lawn mowing is noisy enough; you don’t need any more exposure.

Finally, stop working the moment you notice gas spillage. Even with a metal file, it is still possible to produce sparks, so be watchful of this.

Tools and Materials You’ll Need to Sharpen Lawn Mower Blades

Safety gloves
Safety goggles
Plastic bag
Wire brush
Metal file or angle grinder
Thick and strong wooden plank

Step-By-Step Guide

Step 1: Seal the tank

Unless you’ve run out of gas or have emptied the gas tank, you are going to be working with the lawn mower on its side for a while, so you need to ensure gas doesn’t spill.

To do this, take off the mower fuel tank lid and place a plastic bag over the opening, then replace the lid.

This will prevent gas from leaking out. Some lawn mowers have anti-spill lids, so you may not need this step.

Step 2: Cut off the power supply

The next step is to ensure the lawn mower doesn’t accidentally come on while you’re working. If you are using an electric lawn mower, this means you should remove the battery and/or unplug the cord.

For a gas-powered lawn mower, you need to remove the spark plug cable. Some people just remove the spark plug instead, and either one is fine.

Step 3: Tilt the lawn mower

This is where it usually gets tricky. There are a lot of conflicting opinions on how to tip a lawnmower properly, but the best way is in the video link above.

Of course, the best way to tilt a lawn mower is backward. This will prevent engine oil and gas from flowing where they shouldn’t, like into the carburetor or lawn mower leaking oil from air filter.

However, that doesn’t leave enough access on most lawn mowers, so tilt it on its side with the carburetor and air filter up.

After you tip it, you might need to position scrap wood to provide support so it doesn’t jiggle.

You should use another thick plank to keep the lawn mower blade in place. You can also use locking pliers or any blade lock tool you have.

Read: How should mower blades be installed?

Step 4: Clean the mower deck

Seeing as your lawn mower is on its side; you might as well clean the mower deck. Just like sharp lawn mower blades, a clean deck also reduces drag, which is good for your engine.

Use a wire brush to remove debris from the deck and the blade. If you haven’t cleaned the deck in a while. You might need a bit of water.

Step 5: Sharpen the blade

Now, it’s time to get down to business.

You can sharpen the cutting edge of a lawn mower blade differently, but the two best tools for this type of job are a metal file and an electric grinder or angle grinder.

You can also use a rotary tool with a sharpening stone. A metal file will exert the least stress on the blade, prolonging its lifespan, followed by the sharpening stone, then the angle grinder.

Related: Edger blade sharpener

Whatever tool you use, there are three steps to follow:

i. Grind at an angle

You need to hone the blade following the incline of the bevel. The slope has been calculated by the manufacturer, so it is best not to alter it. To prevent mistakes, that also means you need to move slowly.

ii. Grind outwards

Start on the innermost part of the blade and work your way to the edge. If you use a metal file, you should only file in one direction. With the spinning tools, you can go in both directions.

iii. Only take off the top layer of the blade

Move at a steady pace so that you can constantly monitor what you’re doing. As soon as the blade begins to shine, meaning you’ve removed the top dross, stop. Move to the other blade and follow the same pattern.

When you are sharpening lawn mower blades without removing them, you won’t use a balancing tool to ensure you did it right. That is why you need to be slow and precise.

Step 6: Return the mower to position

Once you’re done with the sharpening process, you need to return things to the way they were.

Ensure you put the spark plug back if you took it out and remove the plastic bag from the fuel cap.

FAQs

What is the easiest way to sharpen lawn mower blades?

The easiest way to sharpen lawn mower blades is with a desk grinder. You will need to remove the lawn mower blade to use this, but this is by far the fastest tool for the job, as it only takes a few seconds. You can also use a blade sharpening tool.

Is it worth sharpening the mower blade?

Yes, sharpening the mower blade will give you the best-looking lawn. Sharp blades cut the grass cleanly, which keeps the blades green and healthy. Dull blades leave jagged edges on the grass that turns brown within a day or two.

Should you sharpen both sides of the mower blade?

No, you only need to sharpen the cutting edge of the mower blade. Even at that, it is only the bevel that needs to be sharpened.

The dull or back side of the blade doesn’t affect the cut, so sharpening it will compromise the strength of the blade.

How to sharpen push lawn mower blades without removing

Sharpening push lawn mower blades without removal can be done by securing the mower on a stable surface, accessing the blades, and immobilizing them with pliers.

Use a metal file or grinder to sharpen the edges, maintaining the original angle. Check for balance and reassemble the mower before testing it.

How to sharpen blades on zero turn mower without removing

To sharpen blades on a zero-turn mower without removing them, follow these steps:

Park the mower on a level surface and disengage the blades.
Use a block to keep the blade stationary.
With protective gloves, file or grind the cutting edges.
Balance the blade if needed.
Re-engage the blades and test the mower.
If unsure, seek professional assistance.

Final thoughts – how to sharpen lawnmower blades without removing

Now that you know how to sharpen lawn mower blades without removing them, the question you should ask is if you should. As much as we like things fast and easy, it isn’t always worth it.

Remember that it is best to remove the lawn mower blades, sharpen them, check the balance then reassemble them.

You should only sharpen it on the mower when it can’t come off or it’s a field emergency.

However you decide to sharpen your blades, there will come a time when you need to replace them. Here is how to know when it’s time to replace lawn mower blades.