A Guide To Sharpening Of Lawn Mowers Blade (+Filer types & How to)

Mowing the lawn is one of gardeners’ most crucial yet exhausting work. But you can make it quicker if your mower possesses sharp blades. For sharpening the blades, you need the correct type of file to do it. What would that be? Here’s what I found. 

The best file should be made of monocrystalline diamond or high-quality carbon metal. Some ideal files are metal, diamond, and ceramic files. The best type of file is a bastard cut mill file. Metal files are preferable due to their cost, availability, and easy usage.

Knowing several types of files are one thing, but understanding which one will work the best for your mower is more critical. Keep reading the article till the end as we will share the ideal files for sharpening mower blades, how to sharpen them, and maintain their edges.

Introduction to lawnmower blades and why sharpening is important 

The blades of the lawn mowers are an integral part of the mower. 

These blades remove the tall and dense grasses from your lawn and keep your lawn neat and appealing. 

The mower blade is made of solid metals to withstand high-speed contact with grass and other objects.

A blunt blade cuts the grass unevenly and destroys its magnificence. 

You have to push your mower harder to keep the lawn neat and attractive. 

Multiple mower types exist, and choosing an ideal one for your lawn can be challenging. You should select one based on your lawn. 

Some common types of mower blades are:

• Straight blades
• Low-lift blades
• High-lift blades
• Mulching blades
• Gator blades

The blade materials, size, thickness, and design used for the mower blades depend on various manufacturers.

Why is sharpening important?

Keeping the lawn mower blades sharp is essential for precise grass cutting and keeping the lawn beautiful and healthy. 

Blunt blades will cause irregular cuts and ruin the beauty of your lawn.

Dull blades tear and shred them, which leads to uneven grass height. 

Not only does this make your lawn unattractive, but it also degrades the grass’s health. 

It further makes the grass vulnerable to pests and diseases. 

But sharp blades can cut the grass clean, flawless, and even. So your lawn will look alluring and clean. 

When grass is perfectly sliced with sharp blades and doesn’t tear, it will heal faster and grow green, luscious, and healthy.

Furthermore, the grasses remain less stressed and can fight pests and diseases. 

So, keeping your mower blades sharp is essential for a clean-cut and healthy lawn. 

Check your mower blades regularly before cutting the grass. 

Different types of lawn mower blades and their sharpening requirements

As mentioned in the previous section, there are five main types of mower blades:

• Straight or medium-lift blades
• High-lift blades
• Low-lift blades
• Mulching blades 
• Gator blades

1. Straight or medium-lift blades

These are the standard blades found on regular mowers and release debris from the sides.  

Despite being straight blades, they have a slight curve on the ends. 

These curves help airflow when the blade turns to suck and cut the grass. 

These blades are primarily preferable for lawns with large grass patches. They can swiftly cut the dense grass. 

There are some drawbacks. 

The first one is that these blades are unsuitable for smaller grasses. 

Secondly, the dense and large grasses can block the chute and limit the storage space in the bag. 

Sharpen the blades once every season or after every 20-25 hours of usage. 

2. Low-lift blades

These blades mow the lawn whose soil has become sandy due to the low suction capacity. The edges are less curly than the previous one. 

The low suction does not allow the grass to grow too high, and the mower blades can easily cut and discharge them to the side. 

The blades are usually 3-4 inches sling and need less energy for the engine. 

One demerit is that these blades cannot suck the debris into the bag. 

Sharpen the blades once yearly or after every 25-30 hours of usage.

3. High-lift blades

The distinctive vertical angles make the high-lift blades different from the others. 

These blades allow enough airflow and help in suction vertically that no other blades can provide. 

The constant circular motion of the blades keeps the grass straight for easy and accurate trimming. 

The blades are available in sizes between 1 and 21 inches and are ideal for lawns with tall grass. 

Despite such advantages, these blades are unsuitable for trimming sand-covered terrains. 

Due to its high airflow, the blades can become prone to pull in the sand, dust, and grass.

The blades use more power and also wear out faster. 

Sharpen the blades 1-2 times per year or after every 10-12 hours of usage.

4. Mulching blades 

Also called a multi-purpose blade, mulching blades have a curved surface that works in various ways. 

The blade raises the grass and then precisely cuts them down. 

The cuttings will then be taken into the deck, where they will be cut into pieces. 

The curve generates air pressure that blows away the tiny grass clipping. 

These blades are also used to fertilize the soil.

However, you cannot cut the dense grass, leading to blockage. 

Additionally, it has low suction, making it unfit for cutting tall and dense grasses. 

Mulching blades should be sharpened once or twice per season or every 20-30 hours.

5. Gator blades 

Like the mulching blades, the gator blades are also ideal for fertilization. 

These blades are adjusted to work more efficiently. 

The inferior blades can generate maximum suction over the grasses and pull them upwards. 

The unique angle at the blade’s teeth will push the grasses toward the sharp edges when the mower cuts them into smaller pieces.

However, these blades are unsuitable for sandy soil and can become dull faster. 

Sharpen them once per year or every 25-30 hours.

Popular file types for sharpening the lawn mower blades

Three popular types of files to sharpen the mower blades are:

• Diamond-coated files
• Ceramic files
• Metal files

Let’s elaborate on their nature.

1. Metal files

Metal files are the traditional files used to sharpen lawn mower blades. 

Most lawn mower owners prefer metal files over diamond and ceramic files. These are affordable, readily available, and also easy to sharpen. 

For the best type of metal file, use a single-cut mill file or a double-cut bastard file made of high-carbon steel. 

They have teeth that help remove materials from the mower’s steel blades.

Before sharpening, disconnect the spark plug and wear protective gear while sharpening. 

I prefer metal files because they are affordable, easily available, and it does the job as expected.

2. Diamond or diamond-coated files 

A monocrystalline diamond or diamond coating file is famous for sharpening mower blades. 

Diamond files are rigid, remove the metal efficiently, and sharpen the blade precisely. 

It makes the sharpening process faster and easier. 

A diamond-coated file will also stop you from over-sharpening and damaging the blade. 

The file will make a clean and even grass cut after sharpening. 

Diamond-coated files are long-lasting, robust, and more precise than the other file materials. 

Diamond or diamond-coated files are more costly than ceramic and metal files. 

However, since it provides multiple benefits, it is worth investing in them. 

One drawback in the diamond-coated files is that the coating can wear down over time. 

3. Ceramic files

Ceramic files are the next popular option in the file list. 

These files are more rigid than the standard steel blades and comprise ceramic particles and synthetic resin. 

The ceramic files are durable and do not clog up the metal fillings. 

Since these files are more robust than traditional metal files, there are chances of potential damage or uneven edges in the mower blades. 

These files are also known to wear out faster when you roughly use them on the steel blades of the mowers. 

Other types of files

There are other files except for diamond, ceramic, and metal files. 

But these files are not ideal for sharpening mower blades. 

They are used for hard materials like ceramics, glass, composites, or carbide. 

Here is a short brief about them:

1. Tungsten carbide files are more rigid and durable, making them ideal for stainless and hardened steel use. 
2. Abrasive files are made up of silicon carbide, diamond dust, and aluminum oxide embedded in a metal or plastic matrix. But it is mainly used on hard materials like ceramic and not the stainless steel blades of the mowers.
3. Ceramic-bonded diamond files are made of diamond particles in the ceramic matric. But they are ideal for harder materials like ceramics, glass, and carbide.
4. Electroplated files are made of electroplating diamond particles over a plastic or metal matrix. These files are also not ideal for stainless steel.

The best file type for sharpening the mower blade is a bastard cut mill file. It is a 10-12 inch mill file used in most gardens. 

You can go for flat files or round files. 

The flat files make a consistent and smooth surface edge in the blades, whereas a round file enlarges the holes and makes the concave curves smoother.

Factors to consider while choosing the best file for sharpening the mower blades

Several factors can affect the selection of the best file for sharpening the mower blades. 

Select the right one for sharpening based on the mower and blade type and your lawn. 

Generally, a bastard cut mill file is considered the best one. But, it is better to consult an expert for the proper guidance. 

Here are some factors that affect the file selection:

• The blade type determines the correct file. For example, rotary blades need a flat file, but reel mower blades need a special reel sharpening kit.
• The file shape determines which file is needed for your mower. You need a flat file for flat blades and a round file for curved shapes.
• The file material is another important factor. A diamond-coated or ceramic file will be durable but may be costly and unavailable. But a metal file is affordable, readily available, and works well.
• The file size can affect the file selection. You need a larger file to cover more blade surfaces quickly. But a smaller file will be fine for smaller blades. 
• The damage level of the blade also affects the file selection. If the blade needs heavy sharpening, use a coarse grit file to remove all the nicks in a shorter period. But, if the blade needs a slight sharpening, you can take time and work with a finer grit file.
• The file grit determines how faster and smooth the blade will sharpen. For example, a coarse grit file can remove the material faster but leaves rough edges which need to be smoothened by a better grit file. A fine grit may remove the material but will be slow.

A step-by-step guide to sharpening the lawn mower blade with a file

Sharpening the lawn mower blade is essential to cut the grass evenly and keeping the lawn clean and attractive. 

But how do you properly sharpen the lawn mower?

Sharpening can be made easy if you know the correct process. 

Below is a detailed step-by-step guide that I follow to sharpen the blades of my lawnmower:

Step 1: Gather all essentials 

For sharpening the mower blades, it is necessary to have the right tools to finish the job faster. 

So, here is a list of tools that I prefer before I begin sharpening the mower blades:

1. Safety goggles and gloves
2. Wrench set
3. A round and a flat file
4. A wood piece
5. A sharpening or polishing stone
6. Clamps
7. A bench vise for clamping the blades
8. Sandpaper

Step 2: Check the condition of the mower blades

Disconnect the spark plug from the lawnmower to ensure the engine does not start in the middle of the sharpening. 

Remove the batteries and unplug them from the main cable of an electric mower. 

Apply parking brakes to keep the lawn mower stationary. 

The blades of a mower become blunt and dull after 30-40 hours of usage, be it constant or in breaks. 

However, it depends on how frequently you have used it and the mowing location. 

When your mower strikes hard objects like rocks or metals, the blades become blunt before 30 hours. 

So, before you sharpen, check the sharpness level to understand the extent of the damage.

Sometimes, you have to replace the blades. 

Tilt the mower to see the blades correctly. 

If your mower is heavy, use a lawn mower table. 

To prevent fuel leaks while tilting, tightly close the fuel valve or empty your gas tank. 

Check for rough edges, cracks, or rust. 

Rotate the blade to examine whether there is any problem with the rotation. 

Mark the blade to remember which way you have to reinstall it.

Step 3: Remove the center nut of the blade and clamp it

After tilting and turning the mower upside down, loosen the center nut of the blade with a socket wrench. 

If it is tough to loosen the nut, spray it with a cleaner spray like WD-40 and wait some time to loosen it. 

If the blade is rotating while removing the nut, use a piece of wood to clamp it to the mower’s underside with C-clamps. 

Now take off the blade from the mower.

Place the blade in a bench vise or sturdy clamp and tighten it to hold it firmly in place. 

The blade will have two cutting edges on the opposite sides of the long metal piece. 

Step 4: Sharpen the mower

Remove the leftover grasses, dirt, and debris from the mower blade. 

If stubborn, use a wire brush or rub the blades with sandpaper.

Once the blades are clean, start sharpening. 

Use the flat file to cut in the forward stroke. Use some regular jabs and keep the right angle with the blade surface. 

The perfect angle for sharpening varies from 30 to 45 degrees.

The mower blades are softer steel. So, nick only 50 strokes with a clean, sharp mill bastard file 10 inches long. 

Chip off the rough edges by going inside it in a regular motion. 

With constant motion, be careful as you go from the corner to the center. 

Repeat it with the other side of the blade. 

Once the dull black surface chips off, your blades are sharpened and look smoother and shiny. 

Angle and bench grinders are also used to sharpen the blades. 

But, these two methods are more complex to control, and you can end up with overheating and damaged blades. 

I prefer manual sharpening with files. 

Step 5: Check the accuracy of the filing angle

Using the file at a correct angle, as mentioned in the manufacturer’s manual, is vital for successful sharpening. 

Always use the file at the blades’ natural angle. 

Too much metal removal and over-sharpening will damage the blade. 

Rub the file at the center of the mower blade towards the tip. 

It will let you have a sharp tip and avoid cracks. 

Give a few pushes with a round file at the blade’s edges. It will round the sharp ties. 

Using a round file will help prolong the blade’s life. 

Ensure not to sharpen the tips too much, or they will wear out sooner. 

Use the round file along the blade length to shape the cutting end. 

Lastly, use a cloth with some cleaner spray and polish the blades. 

Step 6: Balance the blade and reinstall it

The blade should be perfectly balanced during the reinstallation. 

Check the balance by hanging it on a nail over the wall. Observe both sides and file the heavier end if it is lower.

It will prevent vibration and noise from the engine. 

Apply grease to the blade and the central nut, and put the blade back into the mower with a torque wrench. 

Fasten the booths and check that they are correctly tightened.

Reconnect the spark plug and check the mowers. 

If you hear any abnormal sounds, take it to an expert for a checkup. 

If there is no sound and the mower is working fine, your mower is prepared for use. 

Tips and tricks to maintain a sharp lawn mower blade

After sharpening the mower blade, it becomes like a new one. 

Maintaining and caring for the mower blades is crucial to prolong their life. 

So, here are some tips and tricks to maintain a sharp mower blade:

• Clean your mower blade after every mowing session. Remove the grass clipping, dirt, and debris from the blade.
• Check the blades regularly for signs of damage, cracks, chips, or loose connections.
• Sharpen the mower blades at least once or twice a year, based on the usage frequency and the location.
• Keep an extra blade set if you need to replace the damaged blades.
• Replace the blades if they are poorly damaged and cannot be sharpened well. 
• Balance your mower blade regularly to ensure there is no vibration in it. Use a balancer device or place the blade over a wooden dowel and see which side tilts lower. File the lower side and recheck the balance.
• If you are in doubt, call an expert. 

5 suitable files for sharpening mower blades

1. Crescent Nicholson 8-inch Rectangular Double/Single Cut Handy File – Carded – 06601NN
2. SHARPAL 181N Dual-Grit Diamond Sharpening Stone File with Leather Strop, Tool Sharpener for Sharpening Knife, Axe, Hatchet, Lawn Mower Blade, Garden Shears, Chisels, Spade, Drills and All Blade Edge
3. Finder Bastard Cut Mill File Flat, 8 inch Flat Hand File with High Carbon Hardened steel, Ergonomic Grip, Plastic Handle, Flat File for Sharpening Mill or Circular Saws Ideal for Wood, Metal, Plastic
4. Corona FE405506BC0CD Mill Bastard Cut File Carded, 6-Inch
5. Kafuty- 1 8-Inch Flat Mill, Smooth Blade with Ergonomic Handle, T12 Carbon tool steel Edge Metal File Sharpening for Drills and All Edge, Lawn Mower Blade, Garden Shears, Chisels, etc

Final thoughts

Sharp mower blades encourage clean and even grass cutting, neat and attractive lawns, faster healing after cutting, and a lawn free of pests and diseases. Ceramic, diamond or diamond-coating, and metal files are the most popular. 

Ceramic files are rugged and durable, diamond and diamond coating files are stiff and provide enough precision, and metals are affordable and readily available. All of them will adequately sharpen the blades without any issues. 

Consider the factors I have shared while selecting the suitable file for your mower. Follow the guide properly to attain a successfully sharpened mower, and maintain the blade well to prolong its sharpness. 

Reference: Lawnmower Blade Wikipedia