Best Grit for Sharpening Lawn Mower Blades

Best Grit for Sharpening Lawn Mower Blades

Lawn mower blade sharpening is standard practice. It’s the only way to cut your lawn faster and more efficiently.

Moreover, regular sharpening reduces the cost of mowing, and proper sharpening extends the blade’s life.

Unfortunately, there’s common confusion on the best grit for sharpening lawn mower blades. So, we want to explore the most common mower sharpening grits to determine the best grit range.

Best Grit for Sharpening Lawn Mower Blades

60 grit is the sweet spot for sharpening lawn mower blades. This grit level removes enough material to ensure a sharp mower without weakening the blade. However, anything between 36 grit and 80 grit on the US CAMI scale is acceptable to maintain sharp blades without depleting the cutting edges too quickly.

Read: The best mower blades for zero turn to buy

How Do I Make My Lawn Mower Blades Sharp?

Different ways to sharpen a lawn mower blade include a sharpening file, grinding stone, angle grinder, and bench grinder.

Even bench grinders, standard drills, and rotary tools, like a Dremel, can sharpen a lawn mower blade if equipped with the right attachment.

Can you Sharpen Lawn Mower Blades with an Angle Grinder?

Yes, you can sharpen blades using an angle grinder. Indeed, angle grinders are among the best tools for sharpening blades.

They are powerful electric tools that accept various grinding discs to sharpen any blade size or material.

Moreover, angle grinders are versatile and flexible hand-held tools that give you maximum control over the project.

See: DIY Edger Blade Sharpening Methods

What Angle Grinder Disc Do You Use to Sharpen a Lawn Mower Blade?

Grinding wheels (discs) and flap discs are the two main angle grinder wheel types to sharpen lawnmowers.

We’ve come across users asking whether you can use cutting discs too. The answer is a big – NO.

Cutting discs are specially designed to slice through the material, especially wood and metal. So, stick to grinding discs and flap discs unless you wish to slice the mower blade into two.

Grinding wheels are the more popular of the two. However, flap discs are just as effective,  especially when sharpening mower blades. The secret is selecting the right grit size.

Related: The best mulching blade for push mower

What’s Grit Size?

Grit size is the size of the grains found on grinding and flap discs. You see, unlike cutting discs which are wholly metallic, grinding wheels and flap discs consist of tiny abrasive materials glued to a special backing pad.

Common pad materials include plastic and fiberglass. Meanwhile, common abrasive materials are emery, garnet, aluminum oxide, zirconia alumina, and silicon carbide.

The grit size is the physical diameter of each abrasive material. The US uses the Common Abrasive Manufacturers Institute (CAMI) grit-sizing approach, which recognizes #24 to #320+ grits.

Meanwhile, Europe uses the Federation of European Producers of Abrasives (FEPA) chart, which recognizes grit numbers P24 to P400+.

Factors to Consider When Choosing Grit Sizes

Not all grinder wheel grit sizes are equal. Therefore, you must carefully select a grit size for sharpening your lawn mower blades. You want to consider the following critical factors;

  • Mower blade material: Although most lawn mower blades are made from steel, you’ll notice they are different types of steel. For instance, all USA Mower Blades are made from carbon steel. Meanwhile, other manufacturers use mild steel or hardened steel. Alloy and tool steel are other popular materials. You need different grit levels for each material to ensure long blade life.
  • The severity of the problem: How dull is the blade? When did you last sharpen it? Does it have dents and chips along the cutting edge?  These are some of the questions you need to ask. Consider a coarser grit size for extremely dull blades with chips and dents to remove more material.
  • Required finish: How sharp a blade do you want, and how much accuracy does the project require? Finer grits provide a sharper, finer cutting blade for high-accuracy projects. Meanwhile, coarse grits are sufficient for regular projects.
  • Angle grinder power and speed: This is a technical subject. Nevertheless, it’s important. Generally, sharpening at lower speeds requires softer abrasives (smaller grit sizes) due to a higher force per abrasive particle. The opposite is true for higher speeds. So, consider larger grit sizes when sharpening at higher speeds.
  • Other considerations: Three other factors to consider when choosing grinder wheel grit sizes are whether you intend to use a lubricant, the angle grinder’s power/horsepower, and what the manufacturer says. The manufacturer’s guidelines are particularly crucial.

What’s the Best Grit Size for Lawnmower Blade Sharpening?

The standard angle grinder disc coarseness for sharpening lawnmowers is 60 grit, though any grit size between 40-80 grit is acceptable.

However, this doesn’t mean you don’t require coarser or finer grit grinding discs when sharpening lawn mower blades.

Indeed, you often do. Here’s an overview of how to use different grit sizes when sharpening a lawnmower blade;

  1. 36-40 grit – metal removal: This is the perfect grit size for material removal, such as when sharpening rusted, badly dented, or unbalanced blades.
  2. 36-60 grit – edging and chamfering: Use grit sizes within this range to ensure proper blade chamfering (edging or beveling).
  3. 40-60 grit – heavy blending: Blending removes stress concentration points, such as nicks and cracks. It also ensures a uniform blade for uniform mowing.
  4. 60-80 grit – de-flashing and deburring: Sometimes, you may notice burrs at the blade edge after sharpening. A deburring or de-flashing process removes the burrs, so you don’t harm your grass.
  5. 80-120 grit – finishing and polishing: Finishing and polishing aren’t necessary when sharpening your blade for personal use. However, professional service providers need both for customer experience reasons.

What Happens if You Use a Grit Size Too Low or Too High?

An extra-low grit level turns the grinding wheel into a material removal tool. Therefore, it may leave your blades thinner than the standard requirement, rendering them too risky and thus unhelpful.

Conversely, an extra-high grit level turns the sharpening process into a finishing and polishing job. Your blades will be shinier but not necessarily sharper.

Flap Discs or Cutting Discs to Sharpen Lawn Mower Blades

Always choose flap discs for blade sharpening and cutting discs for slicing metal pieces into pieces. A few specialists sharpen mower blades using cutting discs. However, don’t try it.

There’s a great risk of damaging the blade. Moreover, cutting discs easily shatter during such projects, creating new safety hazards. If you cannot find flap discs, seek grinding wheels.

A grinding wheel is almost similar to a flap disc. The only difference is that grinding discs are continuous, while flap discs comprise multiple overlapping flaps glued throughout the backing surface.

What Grit Flap Disc for Sharpening Mower Blades?

60 grit is the magic number when sharpening lawnmower blades using flap discs.

However, you can use slightly coarse grits (40-60) for badly damaged blade edges and finer grits (60-80) for finishing and deburring. Anything beyond this range is unideal.

What Grit Grinding Wheel For Sharpening Lawnmower Blades?

Always use 60-grit grinding wheels for sharpening standard lawn mower blades. It provides optimal blade sharpening.

However, coarser discs are necessary when working on extremely dull blades. Meanwhile, you can turn to finer grits for de-flashing and finishing.

What’s the Best Flap Disc for Sharpening Lawn Mower Blades?

The best flap discs for sharpening lawn mower blades are;

  1. Dewalt DW8311
  2. NEIKO 11142A
  3. Benchmark Abrasives Jumbo Zirconia Type 29 Flap Disc

The 36-grit Dewalt DW8311 is the best flap disc for sharpening mower blades as it’s affordable and reliable.

The 4.5-inch diameter disc is 1.9 inches thick and made from zirconia alumina for 3x faster material removal and 15x longer life. It has a fiberglass backing for extra durability.

The Benchmark Abrasives type-29 disc and NEIKO 11142A are also 4.5-inch diameter zirconia discs. However, they are 40-grit discs.

What is the Best Grinding Wheel for Sharpening Lawn Mower Blades?

For sharpening mower blades, use a 60 or 80-grit aluminum oxide grinding wheel. These wheels are ideal for removing nicks and dullness while achieving a sharp cutting edge. Opt for high-quality wheels designed for tool sharpening.

The best angle grinder wheels for sharpening mower blades are;

  1. Norton Abrasives Model 9000-23 Grinding Wheel
  2. Stens 750-045 Molemab Blade Grinding Wheel
  3. 2PK RBG 1208 Lawnmower Blade Grinding Wheel

The model 9000-23 grinding wheel from Norton Abrasives is your best option. It removes the most steel in the least time for shorter sharpening times.

The 46-grit disc measures seven inches in diameter and is only one inch thick. More importantly, the 1 ¼ -inch arbor hole fits most angle grinders.

Meanwhile, both the Stens 750-045 Molemab Blade Grinding Wheel and 2PK RBG 1208 Lawnmower Blade grinding wheel are eight inches in diameter and one inch thick.

However, the former is 46-grit while the latter is a 36-grit disc.

Best Angle Grinders for Sharpening Lawnmower Blades

The best angle grinders for sharpening lawn mower blades are;

  1. Makita XAG04Z Angle Grinder
  2. Metabo HPT G12SR4 Angle Grinder 4 ½-Inch
  3. Dewalt DCG412B 20V Max Lithium Iron Grinder Tool

The 4 ½-inch 18V Lithium-Ion powered Makita XAG04Z is the pick of the bunch. The automatic speed angle grinder self-adjusts operating speeds and torque for optimal performance.

Meanwhile, the brushless motor eliminates carbon brushes for a cooler operation and longer motor life.

Similarly, the Metabo G12SR4  and Dewalt DCG412B are 4 ½ -inch angle grinders, though the former is corded and the latter cordless.

We love the Metabo grinder for its powerful 6.2-amp motor with 980-watt maximum power output.

Meanwhile, the 8000 rpm Dewalt DCG412B stands out for its quick-change wheel release feature.

Sharpening Lawnmower Blades Using an Angle Grinder: Step-by-Step Guide

The following is a step-by-step guide to sharpening your mower blades using an angle grinder and flap discs.

  1. Unplug the spark plug.
  2. Remove/detach the blade.
  3. Secure and inspect the blade.
  4. Clean the blade.
  5. Install a flap disc onto the angle grinder.
  6. Sharpen the blade, then flip it and sharpen the other side.
  7. Inspect it for balance.
  8. Lubricate the blade.
  9. Reinstall the blade.

Do You Sharpen Both Sides of a Mower Blade?

Not necessarily. It depends on the type of mower blade. Single-bevel mower blades are angled on one side, thus sharpened on one face only. Do not sharpen the other side.

Meanwhile, double-bevel blades are angled on both faces, thus sharpened on both sides. Always sharpen each side depending on the cutting angle.

Can a Mower Blade be too Sharp?

Yes, a lawn mower blade can be too sharp. The blade is considered “too sharp” if you’re terrified to run a finger along the cutting edge.

Unfortunately, overly sharp mower blades are prone to chipping and denting. They also roll more easily, necessitating more frequent sharpening, leading to faster blade replacement.

Do You Need to Sharpen New Mower Blades?

No, it’s unnecessary to sharpen new lawnmower blades as the blades are factory-sharpened and ready for use out of the box.

This applies to blades purchased with the mowing machine and replacement blades. You must unpack the blade, carefully mount it to the lawnmower, and begin mowing.

Can You Sharpen Lawn Mower Blade with Die Grinder?

Yes, you can sharpen lawn mower blades using a die grinder.

To sharpen mower blades with a die grinder, remove and clamp the mower blade, attach the grinding wheel, start the die grinder, and pass the rotating wheel over the blade multiple times.

Carbide and diamond grinding wheels are the best attachments for sharpening mower blades using a die grinder.

Can you sharpen mower blades without removing them?

Yes, it is possible to sharpen mower blades without removing them. You can use a blade sharpener attachment or a grinding wheel to sharpen the blades while still attached to the mower. However, exercise caution and follow safety guidelines when sharpening blades in this manner.

Final thoughts on the best grit for sharpening lawn mower blades

The best grit for sharpening lawn mower blades is 60 grit. However, you typically need to begin at 36 grit and work upwards for an optimally sharp mower that doesn’t damage grass blades.

Avoid coarse grit sizes as they damage the wheel or don’t sharpen.