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How Sharp Should Lawn Mower Blades Be? Tips, Factors, & FAQ

Lawn Mower Blade

When mowing your lawn, you probably strive to get that straight cut that will make your grass even and aesthetically appealing. That can be hard to achieve if your blades are not sharp enough, so it’s good to sharpen them frequently to gain the best mowing results.

Now, you’re probably wondering how sharp the blades should be, which is essential for your mowing job to run smoothly. Keep reading and learn more about the perfect sharpness of lawn mower blades, why it’s so important, and possible occurrences when the blades are too sharp or too dull.

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Why should I sharpen my lawn mower blades?

If you’re someone who likes to have a lush, green, evenly-cut lawn, then you need to sharpen your lawn mower blades. Although they might not seem too important, they’re actually crucial to achieving a good-looking, healthy lawn that will make your exterior stand out.

When the mower blades are not sharp enough, they can lead to several issues that can be hard to treat. It’s always better to be safe than sorry, so ensure that you’re providing your lawn mower blades with regular maintenance to keep them operating well.

Honda Lawn Mower
Photo Credit By: Louiesharpe, Pixabay

How sharp should lawn mower blades be?

Typically, the desired sharpness of lawn mower blades is between a 30° and 40° angle. They must be sharp enough to smoothly cut through the grass without ripping or tearing it. As it can be challenging to achieve these angles, you can compare your blades with blades on a new lawn mower.

They will serve as pointers; every time you sharpen your blades, you can strive to achieve the same sharpness as the new blades. If you go overboard with the sharpening or don’t sharpen the blades enough, you could stumble across a series of issues, which is why it’s crucial to take sharpening seriously.

Can the lawn mower’s blade be too sharp?

Many people think it might be a good idea to over-sharpen their blades to achieve better mowing results. However, the lawn mower blades can turn out too sharp, making their edge more delicate than usual. If that happens, the blade will be prone to folding.

Another common issue when the lawn mower blades are too sharp is that the blade will dull quicker than usual when it comes in contact with stones, rocks, pebbles, and other lawn debris.

What happens when the blades on your lawn mower are too dull?

When your lawn mower blades are too dull, you’ll notice the lack of quality in your cuts. As the blades are not sharp enough, they typically become rounded, and instead of cutting the grass, they rip it by force, which can have a bad impact on your lawn.

Here are the main reasons why you shouldn’t mow your grass with dull lawn mower blades:

  • The grass will become prone to pests and diseases: When you mow your lawn with sharp blades, the cuts will be clean, allowing the grass to heal quickly. On the other hand, when mowing the lawn with dull blades, the grass will get open wounds that will take a lot of time to heal. If that happens, diseases will have an open entryway to attack your lawn, and they could cause significant issues. Also, because of the cuts, the grass will likely attract more pests which can be hard to exterminate.
  • There will be a loss of moisture: When you mow the lawn with a dull blade and rip out the grass instead of cutting it, the moisture from the ground will easily evaporate, turning your once-perfect lawn into dry, yellowish grass.

How to check if your lawn mower blades are sharp enough

When mowing your lawn with a mower with sharp enough blades, it will smoothly run through the grass, creating even, clean cuts. If you notice that your mower is hard to push and leaves rows of uncut or ripped grass, it might be time to sharpen your blades.

Another helpful trick in determining if your lawn mower blades are sharp enough is holding a piece of paper on the side of your mower’s blade when the engine is turned off. Then, you should turn on the engine while slowly moving the paper near the blade. If the blade is sharp enough, it will cut through it. If the blade is dull, it will rip the paper apart.

a lawn mower
Photo Credit By: kikatani, Pixabay

How frequently should I sharpen my lawn mower blades?

Various factors will determine the frequency of blade sharpenings your lawn mower blades will need. At the beginning of each mowing season, you should inspect the blades to ensure there’s no damage, bending, or chipping on the blades. It’s also helpful to check the blades after 10 hours of use to ensure they’re in good shape.

Typically, sharpening once a year is enough to keep your blades as new, but if you’re mowing a larger area, you should check the blades mid-season to verify everything is as it’s supposed to be.

Here are some key things that will affect the need to sharpen your lawn mower blades.

The terrain type

Mowing a lawn on flat terrain without rocks and other sharp objects will make your blade last longer as it won’t hit things while cutting. If the terrain is rocky, uneven, or has a lot of weeds, you’ll likely need to sharpen your blades more frequently.

The lawn size and usage amount

The size of your lawn and the amount of usage of your mower will also significantly impact the need to sharpen your blades. Smaller lawns require less mowing, which will keep your blades in better shape than large lawns that need mowing more often.

The type of metal of the blade

The type of material of your lawn mower’s blade will also be essential when determining how frequently you need to sharpen it. If the blade is made of durable, sturdy metal, it will require less maintenance than thinner metals that can easily chip, crack, or become dull.

How to sharpen lawn mower blades

Sharpening lawn mower blades is not a complex process, but you’ll need specific tools to do the job correctly. The tool list for proper blade sharpening requires you to have:

  • A vise
  • A bench grinder
  • Protective gear
  • A sharpening guide

By following the steps below, you’ll ensure that your blades will be of the desired sharpness.

  • Detach the blade from the lawn mower as you need to access it from both sides.
  • Use a vise to secure the blade and set the adequate angle by using a sharpening guide. You want to achieve an angle between 30° and 40° depending on your lawn mower blade.
  • Use the bench grinder, and start with the coarse wheel to grind the blade slowly with low pressure to remove nicks and chips.
  • Once they’re gone, it’s time to switch to a fine coarse. Again, remember to grind carefully without applying too much pressure on the blade. Try to make the blade as smooth as possible while removing little metal. If you remove too much metal, you could potentially harm the blade.
  • When you finish, reattach the blade to the mower and test it to ensure it is sharp enough.


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A butter-knife sharp lawn mower edge will be the perfect goal you want to aim for to achieve the best mowing results. Ensure that your blade is not too sharp or too dull to prevent lawn damage, and if you don’t have the right sharpening tools, leave the job to a professional that will make your blades look brand new.

Featured Image Credit: Ocskay Mark, Shutterstock


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