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How to Sharpen Mower Blades

by Jackson White
How to Sharpen Mower Blades

Mowing your lawn at the right time is part of the maintenance process. It ensures that the grass is short, even, and neat enough to breed the well-manicured and orderly appearance everyone wants on their lawn. However, you can only get good results if you are working with sharp mower blades.

We all want an aesthetically pleasing lush, green lawn that is almost so flawless. Unfortunately, we cannot control issues such as uneven growth, which is inevitable at one point of growing a lawn. Similarly, we cannot dispute that grass grows faster during the spring season and becomes even bushier than ever. While these instances are inevitable and sometimes quite a nuisance, mowing regularly allows you to keep the grass on your lawn at a uniform level, hence a beautiful yard. The trick is to ensure that you are using a good quality and high-performing lawn mower to meet all your lawn maintenance needs. But, what really is the deal cutter in a lawnmower?

To say the least, the deal cutter in a lawnmower is sharp blades. Matter of fact, sharp blades make the biggest difference in your mowing experience. When grass grows faster and becomes uneven or too bushy, only sharp blades can successfully cut through them without straining your lawnmower. Also, sharp blades make the mowing process less time-consuming and even more effortless. However, there are times when the blades become dull, and the effects are often seen in an ineffective mowing experience and a raggedy–looking lawn. So, how do you sharpen mower blades for better mowing results? Read on to find out!

Why should you sharpen your mower blades?

In general, dull lawn mower blades tend to rip and pull the grass blades. When this happens, the rugged tears left behind weaken the plant. The grass then becomes susceptible to fungal growth and other grass diseases. Dull blades also cause too much stress on the motor when trying to cut through bushy areas on your lawn. If you do not sharpen them in good time, your motor wears out faster than it originally should.

A sharp blade, on the other hand, creates a clean, even, and straight cut. Clean-cut grass quickly recovers hence preventing any disease-causing organisms. Sharp blades also prevent any clogging effects on your lawnmower and are less time-consuming. Considering the fact that sharp blades have more benefits on your lawn, inspect your mower blades at the beginning of the mowing season, check for any dents or bends and check through your lawn for any damages to the grass. If your mower blade has too many dents and bends then you may need to replace it. However, if it is only tearing through the grass, then sharpening it should restore its efficiency.

How sharp should the blades be, and how often should you sharpen them?

While a sharp mower blade is desirable and guarantees efficient results, it is important to know when to sharpen the blades, how often, and how sharp the blades should be. Most lawn owners advise that you sharpen your mower blades at least 2 times and a maximum of 4 times a year. That should be after approximately every 8 mowings.

Even though the recommended time frame for sharpening your mowing blades is after 8 mowings, certain factors may alter the specific time frame. These factors could be the size of your lawn and how often you use your mower.

When it comes to the degree of sharpness, it is common to assume that mower blades with a razor-sharp edge cut grass better, but this isn’t necessarily the case. Your mower blades should be pretty sharp for better results, but you should be able to touch the blade with your hand without getting cut. That said, it is safe to say that the blades should be sharper than a butter knife.

How to Sharpen Mower Blades: A Step-by-Step Guide

No matter the type of lawnmower you own, the blades ought to be sharp at all times. You can either sharpen the blades at home or take them to a retailer who will do it for you. The steps below should guide you if you have chosen to sharpen your blade at home;

Step One: Disconnect your lawnmower

Start by disconnecting the ignition wire on your lawnmower from the spark plug. If you are using a cordless mower, detach the battery back. Doing this significantly eliminates the chance of its engine starting up as you detach the blades. To avoid spilling any fuel when removing the blades, drain the gas tank.

Step Two: Detach the lawnmower blades from the core unit

Sharpen Mower Blades

Tip your lawnmower to the side so that you can access the bolt that holds the blade to the underside section of the mower. Loosen the nut using a large ratcheting wrench and socket. Apply some penetrating oil over the fastener if it seems to rust to make the process easier. After removing the nut, take note of the side of the blade that faces downwards so that you do not get confused when trying to bolt it back later on.

Once you have detached the blade from the primary mowing unit successfully, use a putty knife to clean the underside of the moving deck. Ensure to remove any leaves, mud, clamped grass, and debris that you find. Once done, clean the sides of the mower blade by spraying penetrating oil before scrubbing off debris using a stiff-bristle brush.

Step Three: Sharpen the blade

Clamp your mower blade in a vice at an angle with one of the cutting edges facing upwards. Next, use either your drill-powered blade sharpener or a mill bastard file.

The drill-powered blade features a ¼-inch diameter steel shank, a round abrasive stone, and a flat sharpening guide. Place the sharpening stone into a drill, then squeeze the trigger to run the drill at full speed as you spill the spinning sharpener over the edge of the blade. Move the stone back and forth slowly along the cutting edge at least four to five times as you check the sharpness of the blade. If it is not sharp enough, repeat until all nicks and chips are cleared, and the blade is sharp again. When done with the first side, switch to the other cutting edge and do the same.

When using the mill bastard file, file through the cutting blade until it is butter knife sharp. You can also use a grinder, but the process is a little more technical.

Step Four: Check Blade Balance

In general, sharpening may remove more metal from one side of the mower blade than the other, so you may end up with an unbalanced blade. If your blade is unbalanced, then there will be too much wobbling when mowing that could damage your motor. For this reason, you need to balance the blade.

To do this, slip the blade’s center hole over a nail protruding from any wall then hold the blade in a horizontal position before letting go. If the mower blade remains leveled, then it is balanced enough. However, if one cutting edge rotates towards the side and stops at a vertical or diagonal level, the blade is off balance. To correct this, sharpen the heavier side to remove some metal before retesting it.

For more accurate results, you can use a lawnmower blade balancer specifically designed for this purpose. The balancer comes with a unique design that acts as a leveler, which tells you the heavy side that needs additional sharpening.

Step Five: Re-install the mower blade to its main unit

Once your mower blade is well sharpened and properly balanced, it needs to go back to its original position. Use the same wrench you used to dismantle it to tighten up the bolt. As you do this, ensure to position it correctly, with the right side up.

Once done, reattach the ignition wire or put back the battery pack on your mower, depending on the lawnmower type you own. Afterward, fill up the gas tank and mow your lawn as desired. Always ensure that your mower blade remains clean, not only after sharpening but also after every mowing session. This means that you should wash it regularly and oil it whenever you can. Keeping it clean extends its life and prevents any damages from rust.


Having an extra blade available is a great backup just in case anything goes wrong on your lawnmower, and they are the most appropriate replacement for damaged blades. However, if the only problem you are having is dull blades, sharpening them should restore their functionality. A sharp mower blade will always ensure an aesthetically pleasing and healthy lawn at all times, no matter the season. It is also a guarantee of an effortless mowing session and a longer-lasting lawnmower. Even so, do not over sharpen your blades because scrapping off too much metal may have you incurring a lot more costs for a replacement blade if you have none.

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