The question of “how sharp should a mower blade be?” is one that comes up a lot among yard owners. And that’s no surprise when you consider the implication the blade’s condition can have on not only the cut quality and health of your lawn, but also the longevity of your mower. If it’s either too dull or too sharp, you’re likely to suffer the consequences one way or another.
Tell it to Me Straight: Just How Sharp Should a Mower Blade Be?
While it’s not an exact science and you’re likely to come across different opinions if you ask around online, the general consensus is that your mower blade needs to have a nice straight edge (when it dulls, you’ll see that the edge becomes rounded), but it doesn’t want to be razor-sharp to the touch. If it is, you’ve gone too far.
A very simple rule of thumb and a good reference point for how sharp your mower blade should be is to look at a new blade. Each time you sharpen your blade, your aim is to restore it as best as you can to the same level of sharpness, but no more than that. You’re going for butter-knife sharpness rather than carving knife sharpness.
What Happens When Your Mower Blade is Too Dull?
If you notice the quality of your cut gets progressively worse over time, you can bet your bottom dollar that your blade needs a good sharpening. As we’ve already mentioned, when the blade dulls, the edge on it gets rounded and is no longer able to cut through your grass as it once did. Instead, it achieves the cut by force, ripping your grass blades rather than slicing through them. This is not great for your lawn for a few reasons:
- Loss of Moisture– If you take a closer look at individual blades of grass after passing over them with a dull blade, you’re sure to see ripped, frayed ends. This will allow moisture to be wicked or evaporated from your grass. Definitely not good if a lush green lawn is your goal.
- Increases Risk of Lawn Disease – The cut produced by a perfectly sharpened mower blade will be clean and the grass will heal quickly. But a dull blade produces gaping open wounds that take a considerable time to heal. These wounds provide a direct entry point for disease pathogens to attack your grass, rather like an open wound on your finger could allow bacteria to get in and cause an infection.
And both of these problems will typically have a significant impact on the appearance of your lawn, often causing significant discoloring that’s not nice to look at. And it’s not just your lawn that will pay the price. A less effective blade results in the motor or engine that powers your mower having to work harder, and that extra stress shortens its lifespan, sometimes dramatically in the case of lower quality mowers.
So hopefully you can now see why it’s really important to keep an eye on the condition of your mower blade and ensure that it’s always as sharp as it needs to be.
Too Sharp? Surely the Sharper the Better?
You might think that the sharper you get your lawn mower blade, the better. But that’s not actually true. But it’s not because it’ll have a negative impact on the health of your lawn like a dull blade will. If you were to get your blade as sharp as you possibly could, and then do a side by side comparison against a newly purchased blade, the razor-sharp blade will cut the grass slightly more cleanly. Although, I have to say that we have actually done this, and it’s definitely a case of diminishing returns, as the difference is honestly not that noticeable.
Anyway, the reason why it’s not advisable to rock mower blades as sharp as carving knives is simple; debris. Stones, pebbles, sticks and other yard debris (particularly anything hard) that your mower runs into is likely to create nicks in the edge of the blade, reducing its effectiveness and causing it to dull much quicker compared to a blade that has just the right level of sharpness.
So sharpen it too much, and you’ll likely be pulling your blade out from under the deck and clamping it to your workshop bench far more often than you’d like.
Related Article: Which Side of the Lawn Mower Blade is Up – 3 Ways to Check
At the End of the Day…
…it’s not rocket science, as my grandad would often say after another day of dishing out life lessons as I helped him out on his farm when I was a tad more fresh-faced than I am now. If you can’t remember what your mower blade looked like when it was new, take a trip to any store that sells them and give yourself a quick refresher. Because one look at a new blade and you’ll know exactly how sharp a mower blade should be.