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How to Sharpen a Lawn Mower Blade

Simple DIY Steps To Sharpen Your Own Lawn Mower Blade

This guide explains How to sharpen a lawn mower blade and how to keep mower blades sharp, which is essential to proper lawn care. Without an adequately sharp mower blade – you’ll find it very challenging to get a clean cut when mowing your grass.

Below, you will find Step by Step instructions for sharpening a mower blade, including different methods that may suit you the best.

Whether you’re simply trying to sharpen mower blades with a file, a grinder, or a specialized tool, this is a straightforward DIY mower project that can save you between $50-100 in lawnmower repair costs – each time you do it yourself.

And by the end of this guide, you will be equipped to handle this DIY job easily.

How To Sharpen a Lawn Mower Blade:

 

Step 1: Remove the Lawn Mower Blade

Removing Mower Blade

(As a safety precaution – We suggest you Remove the spark plug first, before removing the mower blade).

Removing the blade from the mower – is a simple matter of loosening the single bolt that holds it to the crankshaft. This bolt will usually be quite tight, but you’ll find that it’s possible to remove it with a sturdy wrench or socket.

Note: If the mower blade wants to “turn” in the same direction while you’re loosening the blade nut, grab a short piece of wood (like a chunk of 2×4)and wedge it between the mower blade and the mower firmly – so the blade cannot rotate.

QUICK TIP:  To make sure you reinstall the mower blade back on the mower – with the right orientation, it is a good idea to use a spritz of spray paint to mark the bottom of the lawnmower blade.

When you reinstall the blade, place the marked side down – toward the ground. That sounds like common sense – But an upside-down blade won’t do you any good 🙂

Step 2: “Clean and Inspect” the Lawn Mower Blade

Knowing how to sharpen lawn mower blades is good, but it won’t help much if your blade is beyond salvaging. Once the blade is off, thoroughly remove grass debris with a stiff brush and give it a visual inspection.

Now, look for any major nicks or severe damage to the blade caused by rocks, roots, or other obstructions. If you see any severe damage, you’re likely better off buying a new mower blade instead of trying to get the old one back into usable condition.

Step 3: “Sharpen” Lawn Mower Blade 

Next comes the actual sharpening – of which there are three (3) different methods to choose from. You can use a Hand file, Power Drill Wheel, or Bench Grinder.

Each mower blade sharpening method is described below.

Hand File Method:

How to file lawn mower blade | Best Home Gear
Filing Mower Blade – BestHomeGear.Com

The first method you can use is to take a hand file to the blade’s edge. Because mower blades are manufactured from softer steel grades, it’s possible to get a sharp edge with a file or a “Manual” mower blade sharpening tool.

To do this, use a hand file to sharpen the blade – start from the top side and work downward toward the cutting edge. Sharpening the blade in this direction – will ensure a sharp, even blade that will hold its edge reasonably well.

Of course, when using a manual mower blade sharpening tool – you use the self-guided tool instead of a hand file – and it delivers the properly filed edge for you.

Power Drill “Wheel” Method:

Power Drill Grinder | Best Home Gear
Using Power Drill Grinder to Sharpen Mower Blade

Another option is to use a powered grinder wheel to sharpen the blade. The grinder wheel attaches to a Power Drill, and although it offers you less control than a hand file, you get quicker results.

If you’re pretty handy with a wheel grinder, you’ll probably be able to manage it without too much trouble.

Note: With the power drill grinder method – you don’t have to remove the blade. With this step, however, if you do not remove the blade from the mower, you cannot “balance the lawnmower blade” when you’re finished.

Many people find this the fastest and best way to sharpen lawn mower blades, and you can easily pick up a power drill sharpener for lawn mower blades at any hardware store.

Bench Grinder Method:

Using Bench Grinder To Sharpen Mower Blade | Best Home Gear
Using a Grinder to Sharpen Lawn Mower Blade – BestHomeGear.Com

The final method for sharpening your mower blade is for the “Die-Hard” DIY people! That is – With the bench grinder approach.

You use a bench grinder instead of a hand file or power drill grinder to hone the mower blade. This is an advanced expertise approach, but if you’re good with a bench grinder, it is a surefire way to get a sharp mower blade edge quickly.

Step 4:   “Balancing a Lawn Mower Blade

Lawn mower blade balancing tool | Best Home Gear
balancing your mower blade

Before putting the blade back on your mower, you should check to be sure it is still correctly balanced. The metal removed during sharpening can cause the blade to fall out of balance, which can translate into poor and uneven cutting – when you put it back on your mower.

To check the balance, you should consider getting a blade balancing tool, which is very economical – a small conical tool on which the blade sits to check the balance of the mower blade.

If the now filed-mower blade remains balanced on the blade balancer cone, it is ready to be reinstalled. If it tilts to one side, you should slowly remove a little metal from the heavy side until it regains proper balance.

Step 5:  Re-Installing a Lawn Mower Blade

Now that your blade has been sharpened and balanced, you can put it back on the mower. To do so, firmly tighten down the bolt that previously held it onto the crankshaft. You can replace the spark plug with the blade reattached, and you’ll be ready to mow again.

Removing Mower Blade | Best Home Gear

 

How to Sharpen a “Mulching” Lawn Mower Blade

Note: In case you’re not sure if you have a Mulching or Regular mower blade – The photo below will show you the noticeable differences:

Mulching vs. Regular Mower Blade | Best Home Gear
Mulching vs. Regular Mower Blade

Many lawnmowers these days are manufactured with Mulching blades that make it easier for grass clippings to be returned to the soil and break down into usable nutrients for live grass over time.

The unique profile can identify mulching blades in the photo (Above).

The basic process of removing, cleaning, and sharpening mulching blade varieties is essentially the same as for a regular mower blade. The only significant difference comes in sharpening the curved portion of the blade that lifts the grass for mulching.

To start with sharpening mulcher blades, you’ll begin with the same basic technique as before, using a file or grinder to work down the beveled portion of the cutting surface from the top.

When you get to the curved portion of the blade, however, it’s best to switch to a smaller file. Using a smaller file will allow you to properly hone the cutting edge on the curved surface, ensuring you get the best possible results from your newly sharpened blade.

As before, you’ll want to balance the blade before reinstalling it, then place it back on the mower. Sharpening mulching blades is a project that can take some practice to get good at, so don’t be too discouraged if you don’t get it perfect the first time.

After a few sharpenings, you’ll be able to quickly and efficiently hone the entire cutting edge of any mulching blade.

Time To Look At A New Mower? Check our review for the Best Self-Propelled Gas LawnMowers you can buy.

FAQ – Sharpening Mower Blades

As with most DIY projects, a few questions seem to come up often – how often to sharpen mower blades and how to do it correctly. Here are some of the FAQs many first-time mower blade sharpeners have.

How Often Should You Sharpen a Lawn Mower Blade?

Before you get down to lawn mower blade sharpening, let’s consider how often you should sharpen mower blades.

A good general rule of thumb is to sharpen your blade after 25 hours for optimal results. So, if your yard takes an hour to mow, you would sharpen your blades once every 25 mowings – or in most cases – once per season.

According to Home Depot – another good measuring tool is to look at your blades of grass after mowing.  If they look brown and frayed vs. green, clean-cut – it may be time to sharpen your mower blade.

For houses with small yards, or you only mow once a week, it’s more practical to sharpen the blade at the beginning of every season as part of your routine mower maintenance.

However, If your yard is large or you mow multiple times a week – a few more sharpenings throughout the season may be in order.

Do New Lawn Mower Blades Need to Be Sharpened?

No. New blades should come with an already sharpened edge, allowing you to use your mower immediately. If you mow and suspect the blade came with a Dull blade, you can consider returning the mower so they can sharpen it – or hey – now you know how easy it is to do it yourself…

How Important Is Mower Blade Balancing?

If you’re going to sharpen the mower blade, you should be sure it’s balanced at the end. An unbalanced blade can affect the quality of your cut and, in extreme cases, could damage your mower’s crankshaft.

Do Electric Mower Blades Need to Be Sharpened?

Yes. Regardless of the “power source,” all Lawnmower blades experience wear and tear that will dull their edges over time.

Does Blade Sharpness Affect How Your Grass Looks?

Absolutely. A sharp blade makes all the difference between a neat, tightly trimmed yard and an uneven assortment of grass blades that will look unkempt.

With a dull blade – the lawnmower will actually “tear” the blades of grass as it is cutting them, resulting in a brown tip appearance.

With a sharp blade – you avoid this problem by actually “shearing” the blades of grass off while cutting them.

Conclusion

Now that you know how to sharpen a lawnmower blade, you’ll be able to improve the appearance of your yard while saving money on costly trips to a lawnmower repair service company.

Do keep in mind that all lawn mower blades eventually wear out. You’ll find it necessary occasionally to replace the old mower blade rather than sharpen it.

In most cases, a quick sharpening will let you make an old blade like new again, and at the same time – your lawnmower will work that much more efficiently – and your lawn will look amazing!

References & Additional Reading:

Kevin
Kevin
Kevin is the author and editor for Best Home Gear. In addition to his work in publishing, Kevin enjoys exploring the Outdoors in Michigan and Arizona, Hiking, Cycling, Fishing, Reading, and Completing Projects for the Home and Garden.

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