How to sharpen a mower blades

You have finally made the decision to replace your mower’s blade.

Maybe you feel it has been completely battered by the rocks or the usual foreign objects that you can’t miss in a lawn.

But upon receipt, it’s painted and doesn’t look razor sharp and so you feel that a round of sharpening may improve the cut.

But should you? Do brand new lawn mower blades need to be sharpened? How do you sharpen mower blades?

Here are a few pointers:

It’s true that a sharp blade will save your time and energy when mowing. It also ensures a super clean cut on top of helping to reduce the spread of infectious lawn fungus.

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But what is a sharp blade and how sharp is sharp?

An excellent cutting edge doesn't imply a small(sharp) angle. In fact, for a healthy cut, what you need is not a razor-sharp feel but a perfect cutting edge.

And a fine cutting edge may even have several angles.

Here is the trick:

If the angle is too acute (at the apex), the blade won't have enough muscle to maintain the collision with overgrown grass and will easily bend, fold, and even nick.

 In any case, a number of users report that once they sharpen their blades "razor sharp" the edge folds over quickly rendering the blades dull after only a few cuts.

To Sharpen or Not To?

As I had mentioned, some gardeners feel that the paint coating make blades to seem not sharp enough and will always sharpen their new blades.

Other lawn owners will say blades are okay just right out of the box and that if you sharpen;they wear out and dull within a few uses.

And the debate continues…

Now, this is what you need to know:

A majority of the blades comes sufficiently pre-sharpened and balanced so you just install them and get down to work.

And the paint surely comes off soon enough.

However, it’s good to check their balance before installing.

I have actually been forced to do a bit of touching up to get blades balanced a couple of times.

That said, the factory edge has an almost perfect bevel angle and will do a thorough job without extra sharpening- at least for the major brands.

When Should You Sharpen Your Mower’s Blades?

To know if your blades are ripe for sharpening, keep an eye on your lawn (after cutting) for these signs:

  • Does the grass look torn and frayed?
  • Are patches of the grass yellowing or browning out?
  • When did you last sharpen it

Always, the grass should remain green and have a smart clean line with minimal tearing.

How to Sharpen Your Lawn mower’s Blade

You don’t lack choices when we come to sharpening:

  • Use a File
  • Use a bench grinder.

Sharpening a Mower’s Blades Using a File

Here is how to sharpen a lawn mower blade with a file:

  • First, detach the spark-plug wire to ensure the engine won’t accidentally roar to life.
  • Turn the lawnmower sideways such that its spark plug will point vertically.
  • Remove the blade. You will use your ratcheting socket wrench to unscrew the nuts attaching it to your mower.
  • Now get a vice (or any other sturdy clamp) and clamp the blade.
  • Take a metal file and sharpen your blade to “butter knife” sharp while maintaining the original cutting angle.
  • Now reinstall your blade and remember to tighten the nuts using your wrench.
  • Finally, lower your mower and fix the spark-plug wire
  • Always wear eye protection and heavy gloves before starting.
  • You should preferably execute only one stroke (either push or pull).
  • You don’t have to file it razor sharp. Just eliminate all the minor nicks and obtain a decent cutting edge.
  • You may mark the outer edge of the blade-just before removing it. This helps you to reinstall it correctly once you’re through with sharpening. As you’ll note, it’s very easy to confuse the sides.
  • Some lawn mowers are designed such that you can access the blade through an opening on the sides making it possible to sharpen lawn mower blade without removing it.

How to Sharpen a Lawn Mower Mulching Blade with a File 

If you own a mulching lawn mower, you may wonder how to sharpen a lawn mower mulching blade with a file or how to sharpen a curved lawn mower blade with a file.

Now, the good news is that the procedure for filing is almost the same and provided that you remember to file at an angle aligned to the beveled edge, the cutting edge will still emerge sharp.

How To Sharpen Lawn Mower Blades With A Bench Grinder

Compared with a file, a bench grinder is easier to use and takes less time.

Here is how to sharpen lawn mower blades with a bench grinder:

  • As usual start by removing the blade. You just repeat the steps I highlighted above.
  • Then, firmly clamp the blade. Now you are ready for sharpening.
  • Before you commence, hold your grinder against the mower’s blade and tip it down or up until the fitted grinding disc (preferably a grinding stone) is perfectly aligned with the optimum angle on your blade.
  • Having confirmed your grinder settings, now turn on the grinder and get down to business.
  • Ensure you hold the disk perpendicular with your blade’s thin edge.
  • Run the grinder until the first cutting sides become sharp.
  • Then remove the blade and flip it over to file the other edge.
  • Keep passing again and again- if necessary- and monitoring progress continuously to avoid narrowing the angle extremely.
  • Now reinstall your blade as we had seen earlier.


  • Take breaks when sharpening as the heat resulting from the friction can melt the blade. You can also cool the blade using water.
  • Don’t apply too much pressure as the blade may end being damaged. Excess pressure also increases the risk of overheating
  • If your blade is cracked, has deep nicks, is bent or is worn thin, sharpening may not help. Consider buying a new one.
  • Improvising a lawn mower blade sharpening jig for bench grinder can help you come up with a straight cutting edge.

Proper angle to sharpen lawn mower blades

Sharpening the blade at the wrong angle will make it to shine without making it sharp. To get the ideal edge, angle your blade toward the grinding disk.

So, what is the proper angle to sharpen lawn mower blades?

In most cases, an angle of about 35 to 45-degreesis recommended as the optimum when sharpening any blade though it varies with your brand.

However, if you can, always maintain the factory angle.

How Often Should You Sharpen?

How frequently you should sharpen depends on:

As a general rule, monitor your grass appearance up close and also far away. If it looks immaculate, your blades are fine.

Otherwise, it’s time for honing.


The question “do brand new lawn mower blades need to be sharpened?” largely depends on the brand and your personal preferences.

But by and large, most of the manufacturers pack their blades ready for use and they will cut neatly right out of the box.

However, in some cases, you may find a blade too dull and be forced to sharpen for a smart cut.


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