Knowing how to sharpen mower blades, and keeping that mower blade sharp are essential parts of proper lawnmower care. Without an adequately sharp mower blade – you’ll find it very challenging to get a good clean cut when mowing your grass.
Whether you’re simply trying to sharpen mower blades with file, a grinder, or a specialized tool, this is a very simple DIY mower project – and one that can save you between $50-100 in lawnmower repair cost each time you do it.
How To Sharpen Mower Blades
Here’s everything you need to know about how often to sharpen mower blades – and how to sharpen a lawnmower blade Correctly when you do it.
You May Be Wondering – How Often Should You Sharpen Your Blades?
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 that you should sharpen your blade after 25 hours of use 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. a 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.
“Five Steps” To Sharpen Lawn Mower Blades
Step 1: Remove the Lawn Mower Blade
(As a safety precaution – Remove the spark plug before starting).
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 your 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.
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 – towards the ground. Sounds like common sense – But an upside-down blade won’t do you any good 🙂
Step 2: “Clean and Visually Inspect” the Lawn Mower Blade
Knowing how to sharpen lawn mower blades is all well and good, but it won’t help much if your blade is beyond salvaging. Once the blade is off, thoroughly remove grass debris from it 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” The Lawn Mower Blade
Next comes the actual sharpening – of which there are essentially three (3) different methods to choose from. Hand file, Power Drill Wheel, and Bench Grinder.
Hand File Method:
The first method you can use is to take a hand file to the edge of the blade. Because mower blades are manufactured from softer grades of steel, it’s possible to get a sharp edge with a file or a “Manual” mower blade sharpening tool.
To do this, using a hand file to sharpen the blade – start from the top side and working 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 simply use the self-guided tool instead of a hand file – and it delivers the properly filed edge for you.
Power Drill “Wheel” Method:
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 a bit 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 to be 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:
The final method for sharpening your mower blade is one for the “Die-Hard” DIY people out there! That is – With the bench grinder approach.
You simply use a bench grinder instead of a hand file or power drill grinder, to hone the mower blade. This is sort of an advanced expertise approach – but if you’re good with a bench grinder – it is a sure-fire way to get a sharp mower blade edge quickly.
Step 4: “Balance” Lawn Mower Blade
Before you put the blade back on your mower, you should check to be sure that 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 a very economical – 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, though, you should slowly remove a little metal from the heavy side – until it regains proper balance.
Step 5: Re-Install The Lawn Mower Blade
Now that your blade has been sharpened and balanced, you can put it back on the mower. To do so, be sure to firmly tighten down the bolt that previously held it onto the crankshaft. With the blade reattached, you can replace the spark plug, and you’ll be ready to mow again.
How to Sharpen a Mulching Blade
Note: In case you’re not sure if you have a Mulching or Regular mower blade – The photo below will show you the obvious differences:
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 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 do get to the curved portion of the blade, however, it’s best to switch to a smaller size 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.
Just 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 Mowers you can buy.
Frequently Asked Questions – Sharpening Mower Blades
As with most DIY projects, there are a few questions that seem to come up often – as to how often to sharpen mower blades and how to do it correctly. Here are some of the FAQ many first-time mower blade sharpeners have.
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 as 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 Balancing?
If you’re going to sharpen the mower blade at all, you should be sure that it’s balanced at the end. Having 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.
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 on some occasions, to replace the old mower blade rather than sharpen it.
In most cases, though, 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:
- How to Safely use a Lawnmower around children
- How to sharpen mower blade with Illustrations from WikiHow
- Have you wondered – Can you cut wet grass with an electric mower?
- Check this article to see the Best Pressure Washers Under $300.
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