You might think lawn mower blade sharpening requires tons of skill. While years of practice will hone your technique, the basic principles to sharpen a blade are rather simple. Follow our DIY instructions and you can have sharp, rejuvenated lawnmower blades in no time at all.
Why Lawn Mower Blade Sharpening Matters
You may think a blade spinning at over 180 mph or more wouldn’t need to be terribly sharp to cut grass. You’d be right. However, a nice sharp blade will slice through grass and allow it to grow in a more healthy manner.
Why does this matter? Because “shredded” grass tips will quickly turn brown, leaving your lawn looking ragged and burnt. The following image helps illustrate this:
For professionals, and people who—quite frankly—just like a nice lawn, having sharp lawnmower blades truly matters for a professional look. This goes triple for species like Fescue which grow more or less straight out of the ground and require frequent cutting.
We know professionals who sharpen their zero turn mower blades every other day.
Ways to Sharpen a Lawn Mower Blade
Many ways exist to sharpen a lawnmower blade. Some of the easiest (and quickest) involve using a grinder. The blades don’t actually need to achieve razor sharpness—they just need to have a decisive cutting edge. It’s this edge that slices through, rather than chops, the grass at high speed.
Using a Small Angle Grinder to Sharpen Lawn Mower Blades
Using a small angle grinder to sharpen lawn mower blades lets you accomplish the task with minimal time investment or cost. You can pick up an angle grinder for very little money, and the process involves matching the angle of the existing blade edge and simply honing it.
Using a Bench Grinder to Sharpen Lawnmower Blades
Similar to the process above, using a bench grinder to sharpen lawnmower blades works just as easily. A bench grinder reverses the process. Instead of moving the grinder over the blade—you move the blade across the grinder wheel. Since many bench grinders include an adjustable table, you can often get fantastic and consistent results using this method.
Try not to over-sharpen the blade. Doing so only results in a too-fragile edge that dulls more easily and weakens the blade. You also want to use quick passes to sharpen the blade. Be careful not to heat the steel too much. If you do, you may inadvertently weaken the hardening process that holds the blade edge.
Balancing the Mower Blade
These methods are rather forgiving, however, you should take care to not miss an important step: periodically balancing the blade. After taking off some metal on either side of the blade and achieving a nice edge, you need to ensure the blade still balances evenly.
To do this, hammer a 16D or similar nail into a wall in your shed or shop and hang the blade from its center point. If it stays balanced, you’re all done. if not, mark the heavy side with a Sharpie marker and take some additional metal off that side by continuing to sharpen it. Most of the time, you can keep a blade balanced by staying aware of how many passes you make with a grinder. Still, periodically check the blade balance to ensure you haven’t drifted too far on one side or the other.
Regardless of which grinder method you use, balance the blade periodically to ensure it stays even.
Other Methods Used to Sharpen Lawnmower Blades
We don’t typically recommend the use of a file when sharpening your lawnmower blades. The process is slow and manual, and the results won’t get you a nicer lawn or a longer blade life. Instead, pick one of the grinder methods above and get to work. If, however, you enjoy using a hand file—by all means, go for it.
If you happen to sharpen mower blades regularly—enough to warrant a faster process—several commercial models do exist to save you time. A newly-created tool from Noracore called the Easy Mower Blade Sharpener (EMBSX) has particular promise. In fact, this tool won a 2019 Pro Tool Innovation Award.
This pneumatic tool drives a die grinder with both a mirror and a camera interface that lets you sharpen the blades on zero-turn mowers without removing them. It takes some finesse and skill to use, so it’s not for everyone. You also need to watch that you don’t sharpen one side more than another or you risk unbalancing the blades.
Some More Considerations
No matter which method you choose to sharpen a lawnmower blade, please be careful to wear proper personal protective equipment (PPE) to protect your eyes, hands, and ears. Grinding mower blades takes little effort and we find it a great entry-level task almost anyone can handle. Still, taking proper safety precautions guards against accidents.
Let us know what you think in the comments below. Do you have a preferred method for sharpening lawnmower blades? Which method works most consistently in your experience? We’d love to hear from you.