How to Sharpen Lawn Mower Blades with a File

How to Sharpen Lawn Mower Blades with a File

Regular blade sharpening allows you to get the most out of your lawn mower. Otherwise, you expend more energy getting the mower around and more gas clearing the grass.

Moreover, a dull blade increases the risk of lawn damage, browning, and diseases. Today, we want to explain how to sharpen lawn mower blades with a file!

How to Sharpen Lawn Mower Blades with a File

  1. Disconnect the spark plug wire or remove the batteries
  2. Remove the lawn mower blade
  3. Clean the blade
  4. Sharpen the lawn mower blade
  5. Balance and lubricate the blade
  6. Reinstall the blade

How Do You Know When to Sharpen Lawn Mower Blades

Since frequent sharpening damages the blade and increases the risk of dents and chips, most homeowners stick to the once-a-season sharpening rule.

However, it helps to break this rule occasionally, especially when you notice the following signs;

  • Uneven cutting height: If a freshly cut lawn has an uneven height, the blade is misaligned or too dull.
  • You mow an area multiple times: You need to sharpen the blades if you need several passes to achieve the correct grass height.
  • You need to push/ride the mower harder: If you expend more energy or use more fuel to get through to the other side of the lawn, you need to sharpen the mower blade.
  • Torn, not sliced grass blades: A sharp blade slices the blades like a sharp pair of scissors. If it tears the blades, it’s blunt.

Dents and bends, a browning lawn, unexplained stalling, and a mower that pulls out chunks of grass are other signs you need to sharpen the blade.

Can You Use a Metal File to Sharpen a Lawn Mower Blade?

Yes, you can sharpen a lawn mower blade using a metal file. Indeed, metal files are among the best tools for sharpening lawn mower blades.

They are affordable, easy to use, and reduce the risk of oversharpening. A 10-12 inch file is your best option.

Read: Do you have to sharpen new lawn mower blades?

How to Sharpen Lawn Mower Blades Using a File

Below we explain everything you need to know to sharpen a mower blade with a metal file.

Safety first

Two steps are critical here. First, you must wear the appropriate safety gear. Why? Because mower blades can accidentally cut you during sharpening.

You must also protect your hands from burns and your eyes from metal splinters. So, wear safety gloves and safety goggles, at the very least.

Secondly, you want to avoid accidentally starting the mower during sharpening. To this end, remove the batteries if using an electric mower, or spark plug wire if using a gasoline or diesel-engine mower.

Tools and Materials

  • Round or flat file
  • Clamps or a bench vice
  • Adjustable wrench or socket wrench

Sharpening Lawn Mower Blades Using a Flat File: Step-by-Step Guide

You can begin sharpening the mower blade once you’ve gathered the basic tools. Here’s how to proceed;

Step 1. Remove the lawn mower blade

This step varies depending on whether it’s a push mower or a riding mower. For push mowers, tilt the equipment on its side to access the blade.

However, this isn’t necessary for riding mowers. Instead, you need to raise the deck to its highest point to access the blades.

Whichever method, the aim is to access and remove the center bolt. A wrench does the job perfectly. When done, remove the blade.

Step 2. Inspect and clean the blade

Now is the best chance to inspect the blade and determine whether it’s worth keeping. If it’s too worn, it’s best to replace it.

For instance, consider replacing badly cracked blades to avert potential accidents. However, if the blade is in good condition, sharpen and lubricate it, then continue using it normally.

Step 3. Clamp and sharpen the blade

Use the clamp or a bench vice to secure the blade to prevent movement when sharpening. Then begin sharpening.

The proper way to sharpen lawn mower blades is from the center to the ends. When done with one half, switch to the other end.

Then turn the opposite side of the blade and repeat. Sharpen both sides at the same cutting angle, ideally 30-45 degrees, depending on the manufacturer’s recommendations.

Step 4. Balance and lubricate the blade

When done sharpening, use a blade balancer to ensure the blade balances at the center hole. This is critical to ensure an evenly cut lawn.

If the blade doesn’t balance, remove material from the heavier side until it balances. Then lubricate the blade using WD-40 or a similar lubricant to protect it from corrosion and rust.

Step 5. Reinstall the blade

Finally, you can reinstall the blade. Make sure you don’t install it upside down. Otherwise, it won’t cut grass. Also, secure it tightly with a wrench to ensure an evenly cut lawn.

Here’s a guide on how to know which way does mower blade go on if you’re unsure. Once the blade is installed and secured, it’s time for a test run.

Best File for Sharpening Lawn Mower Blade

The following are the three best files for sharpening standard lawn mower blades. We’ve included links so you can quickly check them out.

1. Crescent Nicholson 8-Inch Double/Single Cut Handy File

Crescent Nicholson 8' Rectangular Double/Single Cut Handy File - Carded -...
774 Reviews
Crescent Nicholson 8" Rectangular Double/Single Cut Handy File - Carded -...
  • Rectangular shape for smoothing and shaping straight surfaces
  • American pattern file for non-precision material removal
  • Double-cut teeth on one side for rapid removal of material
  • Single-cut teeth on the reverse side for finishing, sharpening, and deburring
  • Forged handle for grip

This is a rectangular-shaped American pattern file for smoothing and shaping straight surfaces.

It’s ideal for non-precision projects, such as mower blades, with double-cut teeth specifically designed for rapid material removal.

Use the single-cut teeth on the reverse side for sharpening, deburring, and finishing.

2. KAFUTY-1 8-Inch Flat Mill File, Smooth Blade

Kafuty-1 8in Flat Mill File, Smooth Blade with Ergonomic Handle, T12 carbon...
63 Reviews
Kafuty-1 8in Flat Mill File, Smooth Blade with Ergonomic Handle, T12 carbon...
  • Tooth Shape: Special tooth shape design, even and smooth, effectively improve the cutting ability.
  • Wide Compibility: Suitable for use on all metal materials including steel, copper, aluminium and many more.
  • Sharpening File: Sharpening file is made of high quality T12 carbon tool steel, which is incisive and durable with high hardness and long service life.
  • Material: The handle grip is made of PP+TRP material, environmentally friendly, non-toxic, non-slip and comfortable.
  • Ergonomic Design: Ergonomically designed handle, comfortable grip, not hurt hand, no fatigue and more efficient use.

This is another excellent metal file with a special tooth shape and design for even, smooth blades.

It works on a wide range of blade types, including steel, carbon, and aluminum.

More importantly, the T12 carbon tool steel file features a single texture with middle-sized teeth to ensure extra-sharp blades without removing too much metal.

3. Finder Bastard Cut Mill Flat 8-Inch Flat Hand File

FINDER Bastard Cut Mill File Flat, 8 Inch Flat Hand File with High Carbon...
338 Reviews
FINDER Bastard Cut Mill File Flat, 8 Inch Flat Hand File with High Carbon...
  • BASTARD CUT FILE FLAT: Finder 8 inch flat hand file is with superior high carbon hardened steel, long lasting and safe teeth and comfortable rubber grip plastic handle. It can be used on sharpening mill or circular saws and ideal for wood, metal, plastic, professional and frequent DIY use!
  • ERGONOMIC DESIGN: The file handle is made of premium quality rubber and plastic materials and features ergonomic shape. It' s no-slip and comfortable to keep a firm and long time hold even in wet and oil conditions and ensures excellent impact resistance, precise and uniform, clear teeth. Rust protection on the piece and the file itself.
  • HIGH QUALITY: The flat hand file is made of high carbon steel with high hardness and high frequency quenching, ensuring strength and logevity. The unique design handle is easy to grip for better control while handling detail work even the Hard-to-Reach areas, make cutting easier from the loss of friction of metal on metal.
  • WIDE APPICATION: Versatile! Our flat cut hand file can be used for processing hard wood, deburring, trimming and chamfering, polishing rough machining, heavy duty usage. Suitable for filing iron and steel. Ideal for garages, factories, engineering, workshop; opportunities are endless.
  • 100% MANUFACTURER MONEY BACK GUARANTEE: Finder Guarantees All of its Products and Tools for Life! Choose us, Choose Quality, Your Best Choice!

Finally, this bastard cut mill file is perfect for sharpening extra hard blades.

The high-carbon hardened steel teeth are durable and long-lasting, while the ergonomic handle ensures maximum comfort.

Use it for deburring, trimming, and polishing your mower blades, besides regular sharpening.

What’s the Proper Angle for Lawn More Blade Sharpening?

Always follow the pre-existing cutting angle when sharpening lawnmower blades. Generally, it’s 35 degrees for standard blades.

However, it varies from 30 degrees to 45 degrees for other blades. Check your owner’s guide for additional information, or call the blade manufacturer for further advice.

Alternatively, check out our guide on proper angle to sharpen lawn mower blades to learn more.

How Sharp Should Mower Blades Be?

Mowers should have aggressively sharp cutting edges but not razor-sharp. Why? Because extremely sharp blades are easily damaged by tough weeds, pebbles, and rough terrain.

So, ideally, keep it butter-knife sharp. It’s sharp enough if it clips grass without tearing the grass blades.

How Often Should Lawnmower Blade be Sharpened?

We recommend sharpening mower blades once every mowing season or every 25 hours of use. The former is ideal for standard lawns with soft, slow-growing grass.

Meanwhile, the latter works best for professionals and fast-growing lawns. You don’t want the blade sharpened too frequently as it necessitates faster replacement.

Alternative Tools to Sharpen Mower Blades

You can use many different tools to sharpen lawn mower blades, including a belt sander and a rotary tool.

However, sharpening stones, bench grinders, and angle grinders are the best choices besides a sharpening file.

Sharpening a mower blade using a sharpening stone

To sharpen a lawn mower blade using a sharpening stone, chuck the stone on a drill, start the drill, and move the fast-rotating stone back and forth along the blade edge.

Run the drill at maximum speed for the best results. It takes 4-5 strokes to sharpen one side of the blade. When done, sharpen the opposite edge.

Sharpening a lawnmower blade using a bench grinder

It’s easy to sharpen mower blades using electric bench grinders. Remove the blade, wear protective gear, and run the blade back and forth against the rotating grinder wheel.

Maintain the same sharpening angle as when you purchased the mower. Alternatively, use a hand-powered bench grinder.

They’re more energy-sapping. However, they’re perfect for one-time projects. A 4 ½-inch hand grinder is your best choice.

See: Simple Steps to Sharpen Edger Blade

Sharpening lawnmower blades using an angle grinder

Finally, angle grinders are some of the best power tools to sharpen lawnmower blades quickly. They’re hand-held, unlike bench grinders which are fixed to a workbench.

However, the mobility provides extra flexibility, allowing you to bring the angle grinder anywhere. In fact, you can use it to sharpen mower blades without removing the blade.

Use either a grinding wheel (grinding disc) or a flap disc to sharpen mower blades. A 36-40-grit disc is the best choice.

When ready, power the grinder tool and run it back and forth along the length of the blade edge.


How do you sharpen lawn mower blades without removing them?

It’s easy to sharpen a lawn mower blade without removing it. First, tilt the mower to its side (if working on a push mower), then grind the top end of the blade at 45 degrees. Only sharpen in one direction, starting from the center outward to the blade ends.

What’s the easiest way of sharpening lawn mower blades?

A bench grinder offers the easiest way to sharpen a lawn mower blade. First, wear protective gear, including eye protection, safety gloves, and earmuffs. Then start the bench grinder and grind the edge of the blade against the spinning bench grinder wheel. It’s a loud process that produces lots of sparks. However, it sharpens the blade in a few minutes.

Final Thoughts

Sharpening a mower blade regularly keeps it in perfect condition for healthier, more beautiful lawns. Fortunately, it’s easy to sharpen a lawn mower blade using a file ( read our next post on how sharp mower blade needs to be?).

Remove the blade and grind the cutting edge back and forth using an 8-10-inch metal file. Then balance, lubricate, and reinstall the blade.