Sharpening lawn mower blades is easy, especially when using hand tools like a metal file. You only need to grind the sharpening file back and forth against the blade edge. That’s all.
However, a common misconception is that you can sharpen the blade at any angle. It’s a major confusion among mower owners that often results in poorly sharpened blades, poorly cut lawns, and, occasionally, blade damage.
Therefore, we’ve compiled this guide to help you understand the correct sharpening angle.
What’s the Proper Angle to Sharpen Lawn Mower Blades?
The correct angle to sharpen lawnmower blades is 30-35 degrees, the same as the cutting angle. The exact figure varies from blade to blade. However, you don’t need to fret, as all manufacturers specify the sharpening angle in the owner manual. Indeed, mowers arrive from the factory with the blade set to this angle.
Does the Blade Sharpening Angle Matter?
Yes, the sharpening angle is very important because it determines the sharpness and durability of the blade. The smaller the angle, the sharper the blade.
However, smaller sharpening angles “consume” the blade much faster. On the other hand, a wider sharpening angle results in a duller blade. However, the blade will last much longer.
When to use a lower sharpening angle
First, sharpen the blade at a lower angle if you want a sharper mower to cut the grass faster and save time.
Additionally, smaller or lower sharpening angles are best for high-precision or high-maintenance projects. They provide sharper blades that cut with less effort, producing perfectly level lawns.
Similarly, consider lower sharpening angles for softer grass and even terrain with fewer obstacles.
For instance, low sharpening angles make sense when mowing fine fescue or zoysia grass lawns.
Also, the lawn must be flat, with no pebbles or stones. A low sharpening angle for mower blades means anything below 35 degrees.
When to sharpen at a higher/wider angle
Consider wider sharpening angles if you want the blade to last longer. It will feel duller (though still sharp enough for the job).
However, the blade wears slowly and thus will serve you for more months or even a few years. Another reason to sharpen mower blades at a higher angle is when working on rough terrain.
A less sharp blade can withstand constant hits and knocks without dulling, chipping, or bending too quickly.
Above all, consider high sharpening angles when mowing a poorly kept lawn. For instance, a less sharp blade makes sense if the lawn hasn’t been mowed in months.
You want a tougher blade to cut down the more mature weed stems easily.
Consequences of Improper Mower Blade Sharpening Angle
Perhaps you’re wondering about the consequences of sharpening the mower blade at the wrong angle. The following are common issues;
- Torn grass: Sharpening the blade at the wrong angle can cause torn grass as the mower grabs rather than clips the grass blades.
- Rugged cuts/uneven lawn: A dull blade sharpened at too wide an angle can result in uneven cuts or a rugged lawn.
- Reduce the risk of grass diseases: Extra sharp or overly dull blades can damage the lawn, triggering various diseases. For instance, leaf blight is common in torn grass.
- Impact on mower health and life: The blade sharpening angle has a direct impact on the life and health of the mower. You may need more repairs or replace the equipment sooner merely because of poor sharpening habits.
- Impact on cost efficiency: The sharpening angle directly determines how much gas you need for the project. It also determines blade sharpening and replacement frequency – both of which cost more.
What’s the Correct Angle for Sharpening a Lawn Mower Blade?
You should always sharpen your lawn mower blade at the same inclination as the cutting angle. The most common lawn mower blade cutting angles are as follows;
15-Degree High Lift Blades
15-degree angled mower blades produce greater airflow to lift grass clippings onto the mower deck using a twist in the blade. Therefore, these are the perfect blades for mowers that bag clippings.
Sharpen them at 15 degrees for the best results.
30-Degree Standard Mower Blades
Standard blades are angled at 30 degrees. The steeper cutting angle guarantees a longer blade life. Also, many blades in this category have a 2-3 degree twist to lift grass clippings onto the deck.
Again, sharpen the blades at 30 degrees for optimum mowing performance.
These are the most durable blades. More importantly, they take on heavier foliage and rougher terrains with less damage. They are also a good choice for sandy lawns to avoid airflow.
Sharpen 45-degree blades at 45 degrees for the best mowing experience.
Combination blades combine two or three blade angles on one deck. For instance, 2-in-1 blades comprise two angles, such as 15 degrees and 30 degrees.
Meanwhile, 3-in-1 blades comprise three angles, such as 15-30-45 degrees. Always sharpen each edge according to the cutting angle.
Lean on how to sharpen the edger blade with our comprehensive guide.
What’s the Best Way to Sharpen Lawn Mower Blades?
The bench grinder offers the best means to sharpen lawn mower blades. It’s a stationary tool affixed to a workbench with a circular wheel that rotates at high speeds.
The first step is choosing the right grinding wheel. A vitrified aluminum oxide grinding wheel is the best choice.
Mount the wheel to the bench grinder, power the machine, and begin sharpening.
Sharpening a Lawn Mower The Right Away: Step-by-Step Guide
The following is a brief overview of how to sharpen your lawnmower blades correctly.
- Wear protective equipment
- Remove the batteries or disconnect the spark plug wire
- Drain the fuel tank and put the fuel somewhere safe
- Loosen the center bolt and remove the blade
- Inspect and clean the blade. Also, decide whether to replace it
- Sharpen the blade using a hand file, angle grinder, or die grinder
- Check if the blade is balanced. To do so, balance it on the center hole
- Lubricate the blade using WD-40 to protect it from rust and corrosion
- Reinstall the blade and tighten the center bolt.
Common Challenges When Sharpening a Lawnmower Blade
Suppose you’re trying to sharpen the mower blade at the appropriate angle but not achieving the desired results. In that case, consider the following;
Are you measuring the wrong angle?
It’s common to measure the back side of the blade, thinking you’re measuring the right angle. Don’t make the same mistake. You need to measure the angle within the blade.
Place the angle gauge over the blade and then measure the acute angle between the underside (the land side) and the cutting section. It should be between 30-45 degrees.
Are you reading the blade angle gauge wrong?
Blade angle gauges show different angles depending on the starting angle. For instance, the gauge may return a 150-degree reading if you start at 180 degrees. To avoid confusion, begin reading at zero degrees.
Is the blade extremely dull?
A reading above 45 degrees is rare. But it’s often a good sign because it signifies a very sharp blade. The same applies to blade angles greater than 40 degrees.
Unfortunately, angles lower than 30 degrees have the opposite effect. It often points to an extremely dull blade. At this point, you should consider altering the blade angle. Alternatively, replace the blade.
Is it a non-standard blade?
If you’ve ruled out all the above issues, you may be dealing with a non-standard blade. For instance, some blades arrive with a 15-degree cutting edge.
Such blades may return a 12-degree or lower gauge reading after a few rounds of sharpening.
How Often Should You Sharpen Lawnmower Blades?
You should get your lawn mower blade sharpened every 25 hours of use. This often translates to once every mowing season for single users with small lawns or every 2-3 weeks for professional lawn mowing service providers.
Alternatively, for homeowners who only use the mower for a tiny lawn in a moderate climate, consider sharpening the mower twice a year – once at the beginning of the mowing season and again at the end of the season.
Unfortunately, more frequent sharpening causes faster wearing, necessitating faster blade replacement.
What’s the best method to sharpen lawn mower blades?
The best way to sharpen lawn mower blades is by using a bench grinder. Begin by finding the right grinding wheel. We recommend a vitrified aluminum oxide grinding wheel. A 60-grit wheel is your best option. Alternatively, use a flat file or grinding stone if you cannot find a power tool.
What’s the best tool for sharpening lawnmower blades
Bench grinders are the best tools for sharpening lawn mower blades. It’s a powerful electric-powered machine with a fast-rotating grinding wheel that easily sharpens most tool blades. Install the right blade and tighten it. Then power the bench grinder and pass the mower blade back and forth against the grinding wheel.
What’s the best angle grinder disc for sharpening lawnmowers?
The Makita XAG04Z is the best angle grinder for sharpening mower blades. It’s a battery-powered electric angle grinder with a variable speed feature for maximum control. Moreover, it features a brushless motor that guarantees a long life of reliable use. The Metabo HPT G12SR4 is an excellent alternative if you cannot find the XAG04Z.
How sharp should lawn mower blades be?
A lawn mower should be aggressively sharp. Sharp blades mow faster, consuming less fuel and putting less strain on the mower. However, it must not be too sharp. For instance, razor-sharp mower blades are prone to rolling (bending during mowing). Overly sharp blades dull faster and are more likely to dent or chip. So, butter-knife sharp is about right.
What angle should my mower blade be?
The angle within the mower blade should be between 30 and 35 degrees, though a few blades accept up to 45-degree blade angles. The exact figure depends on the type of mower and blade. To determine this angle, place the mower blade angle gauge over the blade and measure the angle between the cutting edge and the landside (underside).
The best angle to sharpen lawn mower blades is the same as the cutting angle, typically 30 to 35 degrees for standard blades.
However, it varies from 15 to 45 degrees depending on the mower model and blade type.
Don’t use a different sharpening angle. Otherwise, you may damage the blade and ruin your lawn.