How to Sharpen Lawn Mower Blades

Is your lawn looking ragged and bland instead of healthy and lush? It may have lost its luster as a result of cutting your grass with dull mower blades. You can help bring your lawn back to life by learning how to sharpen your lawn mower blades. The purpose of this guide is to provide you with step-by-step instructions on how to sharpen a mower blade and let you in on some helpful tips, but before we do, let’s look at why sharpening your mower blades is so important.

“Sharp lawn mower blades create a cleaner cut, which improves the health of your lawn. Learning how to sharpen a mower blade is an integral part of maintaining a healthy lawn.”

Why Are Sharp Mower Blades Important?

Cutting your grass with a dull mower blade is sort of like having split ends in your hair. It inhibits healthy and vibrant growth. When you cut your grass with dull mower blades, it tears the blades of grass rather than cutting them. Not only does this contributes to the ragged appearance of your lawn, but it leaves your grass susceptible to diseases. With sharp mower blades, you get a clean cut, which allows your lawn to stay healthy and retain its vibrant luster.

Step-by-Step Guide to On How to Sharpen Lawn Mower Blades

Sharpening a lawn mower blade is not as difficult as you might think. Once you learn the best way to sharpen mower blades, you won’t hesitate to repeat the process two to three times per season. You will soon find that your mower operates better and your lawn remains healthier. There are four main steps involved in the process.

Step One: Preparing to Sharpen the Blade

Preparing to sharpen your lawn mower blade is an essential part of the process. If not done correctly, there is a potential for disastrous results. Follow these steps carefully to produce the best results:

Assemble the Following Tools and Equipment:

•    Safety goggles or safety glasses.

•    Gloves.

•    2×4 wood block 16” to 20” long.

•    4×4 wood block and boards of various thicknesses 12” to 18” long (optional).

•    Paint stick, permanent marker or spray paint.

•    Breaking bar with a socket.

•    Penetrating oil (optional).

•    Wire brush and/or steel wool.

•    File or grinder.

Using safety equipment is an essential element. Wear safety goggles or safety glasses and gloves before and during all the steps.

Disconnect All Sources of Power.

Be sure to disconnect all potential power sources before you begin work on your mower. If your mower is electric powered, be certain that it is unplugged. If your mower is gasoline powered, your best bet is to disconnect the cable from the spark plug. Failure to follow these steps creates the potential hazard that the machine could suddenly start or turn over while the blades are exposed.

Turn the Mower on Its Side.

To get at the mower blade, you need to turn the mower on its side. Either side is fine if your mower is electric powered, but a gas mower should be turned so that the carburetor is facing up. By turning the carburetor up, you prevent fuel from flooding the carburetor, which causes issues when you get ready to start your mower. Placing a block under the motor or engine housing helps to stabilize the mower while you work, you may need more boards of various thicknesses for greater stability.

Step Two: Removing the Blade

Removing the blade requires a bit of torque and a lot of caution to prevent injury. To safely remove the blade, follow these steps:

Mark the bottom side of the blade.

A major mistake many people make when removing lawn mower blades to sharpen them is installing them upside down when they put them back on. A simple way to avoid this issue is by marking the bottom side of the blade with a paint stick, permanent marker or a quick dab of spray paint. Find a place on the blade that is free of debris, so your mark remains after you clean the blade.

Block the blade for removal.

When you get ready to loosen the nut, which secures the blade to the driveshaft, you need to prevent the blade from turning. By wedging a 2×4 under the blade and over the cutter deck, you will pinch the blade so that it won’t turn. Keep in mind that you need to provide resistance from turning counter-clockwise. Place the wedge from the top, right side of the mower deck.

Remove the blade.

Removing the blade takes a significant amount of torque. Make sure that you have a breaking bar that provides plenty of leverage and equip it with the proper socket to fit the drive nut. Place the socket over the nut with the breaking bar a little above the nine o’clock position. Apply downward pressure on the breaking bar to break the nut free. You might have to apply penetrating oil to the area around the drive nut and washers if the nut is particularly stubborn.

Once the nut is loose, unscrew it, remove the blade and the washers. Pay attention to the number of washers and sleeves, as well as their placement, so that you can replace them in the correct order when you reinstall the blade.

Step Three: Sharpening the Blade

With the blade removed from the mower, you can sharpen it in a more comfortable position and do a better job of honing the edge consistently. The following steps will help ensure greater success in sharpening your mower blades:

Secure the blade.

The reason for removing the blade from the machine is so that you can get at it better to sharpen it. Once it is off of the machine, it is best to secure it in a vice. Place the end of the blade with one of the cutting edges in the vice with the cutting edge facing upward. Tighten the vice until the blade is secure.

Clean off the blade.

It is common for grass and rust to cake your lawnmower blade. Though you won’t need to clean off the entire blade (although the edge lasts longer if you do), you want to make sure that you clear all of the debris near the cutting edge so that you have better access to the edge for sharpening. You can use steel wool or a wire brush to clear away this debris. Especially stubborn buildup might require a cold chisel to remove it.

Sharpen the blade.

Most people sharpen lawn mower blades with a flat file, but some also use a hand grinder. Your technique may vary a bit with each tool, but there are several standard guidelines to follow, including:

•    Be sure to maintain the proper angle, typically 45 degrees.

•    Make even strokes from the inside of the cutting edge toward the outside, moving away from you.

•    Do not draw backward, regardless of whether you are using a file or a hand grinder.

•    Once you have finished one edge, flip the blade over and sharpen the other edge. Use the same technique and as close to the same number of strokes as possible, so the edges are uniform.

Bench Grinder Alternative

A bench grinder is particularly useful if the blade is severely nicked, but it also makes for pretty short work when sharpening as well. If you have a bench grinder, you can remove the blade from the vice after cleaning it and sharpen the blade on your bench grinder. Be sure to follow the proper angle of the blade.

Step Four: Reinstalling the Blade

Once your blade is sharp, you need to reinstall it on your mower. To be sure that it is properly installed, follow these steps:

Properly position the blade.

If you marked the bottom of the blade with a paint stick, permanent marker or spray paint, properly positioning the blade is much simpler. Be sure to have all the washers and sleeves on hand and place them in the right order as you thread the nut through the hole on the blade and into the drive shaft. Finger-tighten the nut as far as you can.

Tighten the nut.

Before you can tighten the nut, you need to place your 2×4 wedge on the left side of the mower deck so that you have resistance against clockwise turning of the blade. Secure the socket with the breaking bar above the three o’clock position and apply downward pressure. You need to repeat this several times until you cannot turn the nut anymore.

Prepare to mow.

With the blade secured in place, you can remove your wedge, tip the mower back up onto its wheels and prepare to mow. If your mower is electric powered, you plug it in, turn it on and get started. If your mower is gasoline powered, you need to remember to reconnect the spark plug cable before attempting to start it.

How to Sharpen Lawn Mower Blades without Removing Them

Though you have much better access and it is more comfortable to remove the blade from your lawn mower to sharpen it, you can sharpen it without removing it from the machine. The following steps show you how to sharpen lawn mower blades without removing them from the mower. By not removing the blades, you can complete the task using only two steps.

Step One: Preparing to Sharpen the Blade

Preparing to sharpen your lawn mower blade without removing the blade is similar to preparing to when you removed the blade. If not done correctly, there is a potential for disastrous results. Follow these steps carefully to produce the best results:

Assemble the Following Tools and Equipment:

•    Safety goggles or safety glasses.

•    Gloves.

•    2×4 block of wood 16” to 20” in length.

•    Additional 4×4 wood block 12” to 18”.

•    Wire brush and/or steel wool.

•    File or grinder.

Using safety equipment is an essential element. Wear safety goggles or safety glasses and gloves before and during all the steps.

Disconnect All Power Sources.

Just like when you removed the blade, it is essential to make sure that all potential power sources are disconnected to prevent accidental starting or turning of the blade while you work. Unplug the power cord or disconnect the spark plug cable from the spark plug.

Turn the Mower on Its Side.

Turn the mower on its side, just like above with the carburetor is facing up on a gas mower. Placing a block under the motor or engine housing helps to stabilize the mower while you work, which is far more critical when you sharpen without removing the blade.

Step Two: Sharpening the Blade

Even if you do not remove the blade from the mower, you follow the same steps to sharpen it. However, executing these steps is a bit different.

Secure the blade.

Though you won’t need backward resistance to remove the blade, you need to secure it so that it doesn’t move while you are trying to sharpen it. Wedge a 2×4 under the blade and over the cutting deck to prevent the blade from turning while you work.

Clean off the blade.

You want to knock off any caked grass, rust or other debris from the blade so that you have unobstructed access to the cutting edge.

Sharpen the blade.

Though access is a bit more difficult, use the same technique for sharpening the blade with a file or hand grinder that you would use if you removed the blade. Here is a brief reminder of those guidelines:

•    Maintain the proper angle.

•    Even strokes, moving away from the center.

•    Do not draw backward.

•    Once you have finished one edge, turn the blade over and sharpen the other edge.

Helpful Tips

Following the above steps whether you choose to remove the blades to sharpen them or sharpen them on the mower. However, there are a few tips to keep in mind that help make the process easier. Here are some of the best tips:

•    Knowing When Blades Are Dull. Check the blades of grass on your line and look for signs of splitting and tearing at the tips.

•    Sharpen When the Gas Tank Is Empty. You can prevent fuel loss by emptying your mower’s tank before sharpening or sharpening blades when it is empty.

•    Make Sure the Blade Is Properly Balanced. Be sure that the blades are properly balanced. You will hear funny noises under the mower deck if it is not. Improper balance comes from the blade becoming bent or the driveshaft hole being wallowed out.

•    Dealing with Nicked Blades. A nicked blade does not always mean that the blade is ruined. A nicked blade can be ground out, but you should use a bench grinder for best results.

•    Know When It Is Time to Replace Your Blades. A wallowed out driveshaft hole, a bent or out of balance blade or a blade with nicks beyond repair are all good reasons to replace your blades with new ones.

Summary

If your lawn is looking a bit ragged, the answer to restoring it to better health could be a simple one. Sharp lawn mower blades create a cleaner cut, which improves the health of your lawn. Learning how to sharpen a mower blade is an integral part of maintaining a healthy lawn. Follow these step-by-step instructions for the best results when sharpening mower blades. So get into it and start sharpening those blades!