What Are Common Signs That It’s Time to Sharpen Your Lawnmower Blades?

Last Updated on May 26, 2025 by Duncan

Lawnmowers come in handy, especially during the spring and summer months, when grass appears to grow overnight. To keep up with the frequency of use, you need to service your lawn every two seasons.

To keep your yard tidy, you need to keep your lawn mower blade sharp in addition to regular cleaning, oil changes, and air filter and spark plug checks.

Are you wondering what are the common signs that indicate that it’s time to sharpen your lawnmower blades? Well, there are plenty of signs to look out for. The most common ones are:

Uneven cut

A sharp mower blade is essential for cutting grass cleanly and evenly. Any other outcome could indicate that you need to sharpen your mower blades. If your lawn looks patchy or uneven, even after mowing on a consistent height setting, your blade may be dull or damaged,

Scalping your lawn to reveal bare soil indicates that your lawn mower blade needs sharpening.

Torn grass

Dull mower blades can tear or peel grass tips, leaving your lawn dry and yellowish. You don’t want this, do you? This type of tearing can serve as an entry point for diseases.

A properly sharpened mower blade will create a lift effect, producing a better cut and minimizing lawn damage.

Running out of fuel faster

If your fuel level drops faster than usual, it could indicate that your lawn mower blade needs sharpening. Dull knives make the engine work harder than it needs to, using up to 20 percent more fuel.

To avoid this, you should sharpen your lawn mower blade once a month to protect your lawn while saving electricity.

Requiring more effort to mow

Anyone mowing a lawn knows it takes a lot of effort. However, if you have to push harder or longer than usual, it may indicate that your blade needs to be sharpened.

If your mower is working harder, slowing down, bogging, or requiring multiple passes to get a clean cut, the blade is likely too dull to cut efficiently.

A skilled mower should be able to determine the amount of effort required to mow a lawn with a properly sharpened blade and notice when something is wrong.

Gray appearance

After each mow, inspect your lawn for color changes. It should be vivid green rather than yellow, brown, or boring during the summer. A change in the color of your grass after mowing could indicate that it’s time to sharpen the blade.

The color variances can be obvious or subtle, but the cause is usually the same: your mower blade requires maintenance.

You should note that a lawn mowed with a dull blade often takes on a hazy or muted tone, especially in the sunlight. You don’t want this look on your lawn, do you?

A bent blade

During the summer, inspect your lawn mower blade for any noticeable nicks, bends, or rust. These faults could indicate that you need to sharpen your mower blade. Physical damage or corrosion affects cutting performance and you should address it immediately.

How do you check mower blade sharpness?

You should thoroughly inspect your mower’s blades at the start of the mowing season and after approximately 8-10 hours of use. If you’re wondering whether you should sharpen your mower’s blades, search for the indicators of a dull blade.

Bends, nicks, and/or dents on the blades indicate they are too dull for a clean cut. Make sure the blades are properly sharpened and balanced.

To keep your blades in good condition after sharpening, inspect the lawn briefly before you start mowing.

Remove any pebbles, sticks, or other rubbish in the surrounding area. Watch out for these items that can nick your blade while you mow.

If you’re a new lawnmower owner wondering, “Do I need to sharpen a new lawnmower blade?” The answer is easy. No. New lawnmower blades are ready to use when they arrive and do not require sharpening.

How to sharpen lawn mower blades

What is the secret to having a flawless cut? It all begins with a sharp mower blade. Remember these few simple techniques for sharpening your blade.

• Wear protective equipment such as safety glasses and cut-resistant gloves.
• Disconnect the spark plugs.
• Remove the blade. You can find the instructions in your owner’s handbook.
• Use a metal file to smooth nicks or a grinder to sharpen.
• Work in one direction only; blades usually are 45 degrees.

How Sharp Should a Lawnmower Blade Be?

Blades should be sharp like scissors, not knives. A knife edge will become dull considerably more quickly.

For mower-specific process, consult your owner’s manual.

Depending on how often you use your lawn mower, you should change the blade or blades every one to three years. Always use genuine blades explicitly developed for your mower.

Universal blades may save you a little money but might cause safety hazards such as flung objects. Using blades not designed for your mower can make acquiring the proper mount fit more challenging.

A lot goes into designing and producing a blade, so it’s essential to maintain your mower with the right blades.

Remember to balance the blades.

Checking for sharp mower blades is just one aspect of mower maintenance. Having correctly balanced blades is just as crucial as blade sharpness. An imbalanced blade can significantly impact your entire mower. Vibration puts stress on the engine and cutting deck.

After sharpening your mower’s blades, use a blade-balancing tool to check its balance. If you don’t have a specific balancing tool, hammer a nail halfway into a garage wall and suspend the blade from the center hole.

A blade that hangs horizontally is balanced. If one side drops, use a grinder to remove surplus material from the leaning side. Remove any material at the blade’s end near the sail area.

FAQs

What will dull mower blades do?

Dull blades rip the grass rather than cutting it neatly. This might cause your lawn to turn yellow or brown after mowing as the torn grass tips die.

How does a bad mower blade look?

A defective or dull mower blade frequently exhibits apparent wear, such as nicks, dents, or a lack of sharpness to the touch. Always detach the spark plug before checking the blade to ensure safety.

How can I know if my lawnmower blade is dull?

If your blade has noticeable nicks or dents or does not feel sharp to the touch, it is probably dull. Remember to detach the spark plug before checking the blade.

How long does a lawn mower blade last?

A lawn mower blade’s lifespan is determined by several factors, including the type of grass being cut and the frequency with which you mow. If the blade is sharpened every 20 to 25 hours of use, it has an operational lifespan of about 100-200 labor hours.

However, examining your blades at least once a year is wise.

When should I replace my lawnmower blades?

Replacing them once a year will produce the most outstanding results, although they may need to be replaced sooner due to damage from rocks, pebbles, and other debris; if you use them professionally, replacing them twice a year is preferable.

Regular balance and honing can increase the blade’s life, but general wear and tear will highlight the need to replace your mower blades regularly.