How to Change a Lawn Mower Blade | Guide To Restoring Efficiency & Speed of Mowing Grass Safely

A lawn mower is an efficient garden tool that keeps your yard trim and clean. It's quite easy to forget that the blades of your lawn mower can get rusty and old. Most times, you start to look for how to change a lawn mower blade when it gets worn out. At this point, it becomes challenging for you to cut through grass effectively.

Blunt blades merely butcher your grass, making your lawn more vulnerable to disease, patchiness, and dull/brown appearance.

On the flip side, a sharp blade keeps your grass clean and green. You'll also save a ton of time and gas when you have a sharp lawn mower, to learn how to change a lawn mower blade and the benefits of replacing a lawn mower, keep scrolling.

The Importance of Changing A Lawn Mower Blade 

importance of changing a lawn mower blade

Wear/tear is normal for blades, primarily if you only use one blade consistently. A dull blade will rip grass rather than cut it smoothly; you'll end up wasting more time and fuel mowing your lawn. You'll also need to change a lawn mower blade because of these following reasons.

•    Ragged Grass: Dull blades cause shabby tears that can damage grass and encourages grass disease.

•    Sticks and Rocks: If you're a frequent "mower," then you've probably hit a couple of stones, sticks, bottles and any litter in your front yard. These hits and whacks reduce the strength of your blade, as well as chip the edge.

•    Patchy Lawn: A lawn mower with a weak and blunt blade will often leave irregular spots in your lawn.

•    Frequent Mowing: A dull blade will have you mowing the lawn more often than you need to.

Inspecting Lawn Mower Blade

Before changing the blade of your lawn mower, you'll need first to examine the condition of the blades. You can check the blade by tilting the mower up with the front wheels pointing up and the handle laying flat on the ground or bench. This position ensures that oil does not flow to the wrong place, which can cause even more problems.

Any sign of a crack, bend or thinned out edge or holes in the blades file mean that you need to replace the blades. If your blades are still thick and not bent out of shape, they might just need to be sharpened not replaced.

As discussed, if your lawn mower is leaving your yard looking uneven or the tip of the grass blade is torn and not perfectly sliced, you should consider changing blades. The torn tips will make your grass unhealthy, causing them to lose their color to a poor brown hue.

Sharpening Lawn Mower Blades 

Before heading over to your local hardware store for a lawn mower blade replacement, check if your blades are still thick, even though they lack precise and neat cutting, sharpening your blade might be a better and cheaper alternative. To sharpen the blades, you'll need to;

Step 1: Loosen to get a socket or wrench that fits the blade nut. If the nuts are a bit tougher, you can get a breaker bar or a penetrating lubricant. Two clamps, one block of wood as well as an angle grinder with a metal grinding blade will be needed.

Step 2: Disconnect the spark plug wire.

Step 3: Use a piece of plastic to cover the gas cap and prevent gas from escaping through the vent hole when the lawn mower is tipped.

Step 4: Tilt the mower on its side to make the carburetor face up.

Step 5: Secure a block of wood to the side of the mower to prevent the blade from turning while you loosen it.

Step 6: Make sure you note down the grass side of the blade, to prevent reinstalling it the wrong way. With the use of a socket wrench or breaker bar, turn the nut counter-clockwise to loosen it (soak it in penetrating oil for an hour if it's too stubborn).

Step 7: Put on gloves, a face shield, hearing protection, and a long-sleeve shirt before grinding for protection. You should also clamp the blade down securely to the edge of the bench or on a metal vise.

Step 8: Secure the grinder against the blade and tilt it up and down until the grinding disc aligns with the angle of the blade.

Step 9: Maintain this angle while grinding. Apply light pressure to the grinder to avoid overheating the blade or "overriding" it.

perfect backyard with sharp mower blades

Make sure not to overheat the metal. Otherwise, the blade will turn dark blue or black, become fragile, and end up getting blunt. The point is to make it as smooth and dent-free as possible. An overly sharp edge will become dull again and damage easily.

Pass the blade repeatedly on the grinder, applying light pressure and making sure to check for progress.

Excessive scratches and nicks can be sorted out by holding the grinder at a right angle to the blade and smoothening over the edge of the blade.

Blades with deep marks and cracks, or which are bent or thin, should not be sharpened. It is a sign that you need to replace the blade with a new one.

The rule of thumb is to sharpen the blade every 25 hours of cutting your lawn.

If you're not a fan of grinders or blades, you can give your blade to a local hardware store to get it sharpened at a low cost.

How to Balance A Lawn Mower Blade 

Once you've sharpened your blade, you'll have to balance it into an appropriate position for top-notch performance. However, note that this should only be done after you've sharpened the blade to renew its performance.

Lawnmowers spin between 3500 and 4000 rpm, which is about 60 revolutions per second. When lawnmower blade knives are out of balance, this can cause strain on the lawnmower blade shaft and cause it to break. In the long-run, this can be dangerous to the person mowing or people close by.

To get the best balance, you'll need a special balancing tool. This is typically the balancer component for mower blades, and it is one of the best tools if you mow frequently. A balancer is shaped like a cone, and it balances the mower blade on its tip.

how to replace a lawn mower blade easily

To use it, place the blade on the balancing device to check for balance. Once it's on, watch if a side tilts downwards. When you find one, it means that one end of the blade is heavier than the other part.

Blend the end of the blade that is heavier with the use of light motions. After this, recheck the balance. If you find that one end is still dropping, then continue with the light grindings.

How to Replace A Lawn Mower Blade

When your blade is beyond repair, it's time to look for how to replace a lawn mower blade. If this is your first time replacing a blade, it is best to know which blade fits your lawn mower.

There are three types of lawn mower blades you can purchase; high-lift, medium-lift, low-lift, and mulching blades. If you already know the kind of blade you want, then you're free to skip this part and jump to the next section to learn how to remove lawn mower blades.

Low-Lift: A low-lift blade is under ¾ inches, and it requires less power. It also produces less noise and dust, and it has more durability. These blades are suitable for sandy and dusty terrain, both of which require zero high lift and suction.

However, note that when excess sand and dust get into the deck, they can cause premature wear on the blades and equipment.

Medium-Lift: A medium-lift is ¾ inches to 15/16 inches. It typically has a straight edge with standard discharge. In addition to that, it has a bit of an upward angle on the edges, which is excellent for horsepower.

Just as its name implies, it produces a medium lift, and it doesn't need as much strength as high-lift blades.

High-Lift: A high-lift blade is 1 inch to 1-3/16 inches, and it is best for bagging clippings. The blades also have a very prominent angle on the corners, which helps to generate more lift. This blade is suitable for lifting grass clippings for a polished lawn look, and it requires more horsepower, especially when cutting tall or dense grass.

However, note that this blade isn't ideal for sandy or dusty soil surfaces. When sand or dust gets into the deck, it causes wear and tear on the blades and equipment.

Extra high-lift: This type of blade is usually 1-1/4 inches and up and has the most suction. This is the best blade for cutting overgrown and compact lawns but requires more power out of all the other blades. It is not suitable for sandy or dusty surfaces. Any sand or dust that gets into the deck will ultimately speed up the wear of the blade and equipment.

Mulching blades: These are also known as 3-in-1 blades because they can be used to bag, discharge, and mulch grass clippings. Mulching blades are curvier, and they have a more pronounced cutting edge. This allows the blade to cut the grass, bring it into the deck for further cutting, and toss it on the lawn into tiny pieces. Grass clippings from mulch blades are used as natural fertilizers for soil and plants.

If you still struggle with finding the right fit for your blade, take your old blade to a store that deals with replacement blades and find a suitable alternative. For newbies, you can read our self-propelled lawn mower reviews and best mower for hills, for other options.

How to Change Lawn Mower Blade 

When it comes to removing a lawn mower blade, you'll need to first get lawn mower blade removal tool from a hardware store before proceeding to these steps on how to remove a lawn mower blade.

how to change lawn mower blade

Step 1: Remove the spark plug wire, to shut down the engine. Tilt the mower on its side, facing the air filter up which prevents oil from dowsing the filter.

Step 2: Safety first, so put on a pair of gloves. Hold the lawn mower blade by sticking a 2x4 block between it and the mower deck. Loosen the fasteners securing the blade to the drive a shaft with a combination wrench. There's usually a bolt or two, with or without a special washer.

Step 3: Take a picture of the blade assembly once you've removed it, so you can put it back together correctly (usually, the user manual has pictures for this step). This is an important step, especially if you don't know how to balance a lawn mower blade. From there, remove the blade, blade support and blade bolt off the crankshaft.

Step 4: Put the new blade, blade support, and blade bolt on the crankshaft and use your hands to tighten the blade bolt into it. Again, it is essential for you to know how to balance lawn mower blades (or at least, get the help you need).

Tighten the blade bolt to 500 inches-lbs. with a torque wrench.

Step 5: Pull your blade into more of an upright position, push the spark plug wire back onto the spark plug, and it's as good as new.