Which Side of the Lawn Mower Blade is Up?

You recently bought a new mower blade or sharpened your existing blade, put it back on your lawn mower, and rolled it out onto your lawn with a smug little grin, visualizing the impeccable cut you’re about to witness (poetry in motion…). But then you fire her up and to your horror, your mower is cutting worse than before. “But the blade is sharper than ever” you cry!

If you’re facing or have faced this scenario, it’s highly like that when it came time to installing your blade, you put it on the wrong way round.

If you didn’t know before, you now realize the importance of knowing which side of the lawn mower blade is up.

Which Side of the Lawn Mower Blade is Up? (The Short Answer)

Regardless if you have a mulching blade vs. a regular blade, all lawn mower blades have to be orientated the same way when installing a blade on a lawn mower. The flat side of the blade should always be facing the grass, and any twists or mulching teeth should be facing the lawn mower deck.

How to Know Which Side of the Lawn Mower Blade is Up?

If you have no idea what you’re doing, you’ve got a 50-50 shot at guessing right. And those are not bad odds. But there are a few very simple tricks that you can use to get it right 100% of the time. I’m not really a betting man, but a 100% chance of winning sure sounds good…

Here are my favorite tricks to figure out which way a lawn mower blade goes on:

It’s Stamped on Your Blade

This can be one of those “duhhh” moments. Lots of mower blades have something like “Grass Side” stamped directly onto the blade. Have a look to see if this is the case with your blade. If it is, you’ve just hit the jackpot as you now know for sure which side is up. If you don’t see anything stamped onto the metal, there are still a number of ways to tell which side of the lawn mower blade is up…

Sharp Side of Your Blade Closest to Ground

If you look at your blade, you’ll notice there’s a sharp side (the cutting edge) and a blunt side. The blunt side will usually have a raised edge, rather like wings. This raised edge is what “lifts” up your clippings once they’ve been cut into the air vacuum of the deck so they can be directed into your grass catcher or out the discharge chute. So when installing your blade, you want to make sure these “wings” are pointing upwards towards the underside of your deck, and the sharp side of the blade is the side that is closest to the grass.

Sharp Side of the Blade Moves Towards You

When you have your mower tipped over and you’ve attached the blade and tightened up the bolt, there’s a quick test that you can do to help you figure out if you’ve got an upside-down mower blade or you’re good to go. With the mower tipped on its side, move the blade towards you (the direction of the blade will depend on whether the mower is tipped on its right side or left side. If on the right side, move the blade in a counterclockwise direction, and if on the left side, move it in a clockwise direction.) When doing this, this sharp edge of the blade should be the edge that leads. If it does, then you have the correct lawn mower blade position. If not, you need to flip it over.

Sharpening Your Blade: A Quick Trick to Re-Install the Right Way Up

If you know for sure that your mower blade is the right way up before you remove it to sharpen it, you can mark the grass side yourself to avoid any confusion when it comes time to re-install it. I’ve done this myself in the past when using a blade that wasn’t stamped. A quick spray of paint and you’re done. Simple!

How to Know if Lawn Mower Blade is Upside Down?

If you’re perceptive, it’s pretty simple to come to the conclusion that your lawn mower blade is upside down. You see, it’s all in the cut. As I mentioned at the beginning of this post, if you change your blade out for a new one (and no, new blades don’t need to be sharpened) or you sharpen your existing one, you do so to achieve a better cut.

But what you’ll notice if you install this blade the wrong way round is that the quality of the cut your mower gives you actually gets a lot worse. And that makes a lot of sense, because it’s now using the blunt edge to cut the grass (well, more like hack). Imagine if tonight, when you are preparing dinner, you chop your veggies up using the blunt edge of your knife. I’d put money on it being a mess! The same goes for a lawn mower blade that is the wrong way up.

So if you see that your grass is being hacked to pieces as opposed to a crisp cut, you can bet your bottom dollar it’s because your blade is the wrong way up. And that’s something you’ll want to remedy right away!

Why You Definitely Don’t Want to Continue to Cut with the Mower Blade Upside Down

Cutting with the blade incorrectly installed is a big no-no. And honestly, it’s something a lot of people do for long periods of time without ever realizing it. Many people get rid of mowers saying something like “it cuts like s***” when all along they were cutting with the blunt edge of the blade.

I’ve literally picked up a couple of mowers for free like this, flipped the blade over (and because they had it the wrong way round, the cutting edge was virtually new!), and the mower cut beautifully.

But here are a few reasons why you’ll want to correct the lawn mower blade position right away if you realize it’s upside down:

Your Grass Will Suffer

I won’t drone on here as I’ve already touched on this, but cutting with the wrong side of the blade is akin to hacking your grass, not cutting it. Tearing it like that weakens it and leaves it wayyy more susceptible to lawn diseases and pests.

You May Bend Your Mower Blade

Remember those “wings” we mentioned earlier. With a blade that’s the wrong way up, they’re pointing toward the ground, meaning the chances of you hitting a stone, rock or stump are much higher, especially if you tend to cut your lawn short and have the deck closer to the ground. These kinds of impacts can unbalance your blade, or worse still, bend it. And a bent blade ain’t no good. You’ll need to buy a new one.

Bent/Broken Crankshaft

– I don’t want to get all doom and gloom here, but in the worst-case scenario, if you hit something like I just described, you could bend or even break your mower’s crankshaft. And if you do that, you’ll be looking for a new mower. Because having a crankshaft straightened or replaced these days is just as expensive (and sometimes not even possible) as ordering a brand new mower.

Final Thoughts: Be Careful When Installing Your Mower Blade

I hope I’ve stressed enough that it’s really important to pay close attention to which way the lawn mower blade goes on. It’s a simple mistake to make, but one that can be costly both for you and your lawn. And it doesn’t need to be that way when there are some very simple tricks to ensure you have the correct lawn mower blade position.