How To Adjust Lawn Mower Blades (Expert Guide)

You need to know how to adjust lawn mower blades. It’s a simple process, but it can make a huge difference in the health of your lawn and the performance of your mower. 

Follow these steps for easy blade adjustment:

How to Sharpen a Lawn Mower Blade
Proper maintenance and adjustment of lawn mower blades are crucial for maintaining a healthy lawn and prolonging the mower’s lifespan.
There are various types of lawn mower blades, including standard, mulching, and high-lift blades, each with their unique benefits and uses.
You can adjust your lawn mower blades to achieve the desired cutting height, balance, and sharpness, but it’s essential to follow the manufacturer’s instructions and safety precautions.
Sharpening and replacing lawn mower blades can improve your mower’s performance and reduce soil and grass damage, but it requires attention to detail and the right tools.
Understanding the common issues that can occur with lawn mower blades, such as unbalanced blades, dull edges, and damaged components, can help you troubleshoot problems and prevent them in the future.

Ensure Your Mower Is Turned Off And The Engine Is Cool

Before you begin adjusting the blades, make sure your mower is turned off and the engine is cool. Check the oil level, tire pressure, and air filter. 

Next, remove the spark plug from its housing and inspect it for signs of wear or damage. Finally, attach a torque wrench to one blade’s tightening nut (use a socket wrench if you don’t have one)

 If you’re having trouble starting your lawn mower, it may be because of a loose or damaged throttle cable. Our detailed guide on adjusting the lawn mower throttle cable can help you troubleshoot and fix this common problem.

Disconnect The Spark Plug Wire To Prevent The Motor From Accidentally Starting

Disconnect the spark plug wire to prevent the motor from accidentally starting.

Remove the blade, if necessary (depending on the model). To remove it, use an adjustable wrench or hex key allen wrench and rotate counterclockwise until you can slide it off of its spindle.

Inspect for damage and measure your mower’s throwing distance by observing how far your lawnmower throws clippings when given maximum power (refer to manufacturer’s specifications).

Remove bolt cover, if necessary (depending on the model). Some models of lawnmowers have a bolt cover located at the base of their blades that must be removed before adjusting them; this may require using an adjustable wrench or hex key Allen wrench depending on your particular model of lawnmower

Disconnect Spark Plug Wire to Prevent Accidental Starting

Preventative MeasuresDescription
1. Turn Off the MowerAlways turn off the lawn mower before attempting maintenance or repairs.
2. Locate the Spark PlugRemove the spark plug cap and locate the spark plug wire.
3. Disconnect the WireCarefully and firmly pull the wire off the spark plug.
4. Inspect the WireCheck the wire for damage or wear after removal.
5. Store SafelyStore the wire safely away from the spark plug and engine until reconnecting before use.

This table provides a step-by-step guide on how to safely disconnect and remove the spark plug wire to prevent the lawn mower motor from accidentally starting during maintenance or repair.

Remove The Blade

  • Remove the blade nut by turning it counterclockwise until it stops and then pull it off of the blade.

Remove the blade by lifting it up and out of its clamp with your hands, then sliding it off of its shaft so that both ends are sticking straight up into the air like a pair of swords on either side of you (the flat edge should face away from you).

Remove the spacer (a metal washer) from between your lawn mower’s blades by pulling it out with pliers or prying at one end until it snaps off in half and then pushing aside any remaining pieces before moving on to step four below! 

Proper valve clearance is critical for maintaining your lawn mower’s performance and prolonging its lifespan. Learn how to check and adjust your lawn mower’s valves with our step-by-step guide on adjusting lawn mower valves.

Inspect For Damage

If you’ve got a bent blade, it won’t cut evenly and can cause your mower to vibrate. The best way to check this is by placing the flat side of a ruler against the top edge of the blade while it’s spinning.

 If there are any high spots that stick out more than 1/8 inch (3 mm), then you’ll need to replace the blade.

When checking for balance, look at both sides of the tip with equal space between each tooth when compared to its neighbor on either side. 

If they’re not equal distance apart, replace them both don’t just replace one side if only one seems off-kilter.

Finally, check for sharpness by running your finger along each individual serration at an angle close enough so that it cuts into your skin slightly but doesn’t break through all layers

If you feel no resistance or pain from these serrations as they pass over them (or if they do cut into flesh), then it’s time for a replacement!

Inspect for Damage

Inspection StepsDescription
1. Turn Off the MowerAlways turn off the lawn mower and unplug the spark plug before attempting maintenance or inspections.
2. Remove the BladeRemove the blade by using a wrench or socket set to remove the bolt or nut that holds the blade in place.
3. Visually Inspect the BladeInspect the blade for any visible signs of damage or wear, including bent edges, cracks, or chips.
4. Check for BalanceCheck for balance by placing the blade onto a nail or similar sharp object in the center hole and holding it up. If the blade tips to one side or the other, it is unbalanced, and you should consider getting it fixed.
5. Use a Straight Edge to Check for StraightnessCheck the straightness of the blade by holding a straight edge along the blade’s length. Look for any areas where the blade is bowed or uneven.
6. Use a Ruler to Check for Bent EdgesCheck for bent edges by holding a ruler against the top of the blade while it’s spinning. Look for any gaps between the ruler and the blade.
7. Replace or Repair as NeededDepending on the damage, you may need to replace the blade altogether or take it to a professional for repairs.

This table provides a step-by-step guide on how to visually inspect and check a lawn mower blade for damage, balance, and straightness. By following these steps, you can ensure that your blade is in good condition and performing optimally.

Measure The Blade’s Throwing Distance

To determine the distance a blade throws, measure from the cutting edge of your mower to the ground. This is called the throwing distance. 

In general, the throwing distance should not be more than 1/3 of your mower’s overall height. For example, if your lawnmower is 3 feet high, then its blade should not throw any higher than 9 inches off of the ground (3 x 3).

If you find that your blade is throwing too high or low, here are a few things that may be causing this problem:

  • You installed it incorrectly (re-check the steps above)
  • Your blades need sharpening

Want to fill in some bare spots in your lawn or simply increase its overall density? Our guide on adding grass to your lawn offers several practical tips and techniques, including overseeding and sodding, to help you achieve a lush, healthy lawn.

Remove The Bolt Cover, If Necessary

If you have a bolt cover, remove it before proceeding to the next step. To do this, use a screwdriver to loosen the bolt and then lift up on the cover with your fingers. 

If there is no bolt covering your blade, skip this step and go on to Step 2.

Loosen The Blade Bolts

Use a hex key to loosen each blade bolt by turning it counterclockwise. Do not over-tighten the blade bolts, as this can lead to the breaking or cracking of your lawn mower blades.

Tighten the blade bolts with a screwdriver and nut driver wrench, if necessary. If you have an older model of lawn mower with no hex key available, use a screwdriver and nut driver wrench to tighten each blade bolt by turning it clockwise until it is snug against its corresponding hole in the hub of your lawn mower’s axle housing plate

Cutting your grass at the right height is important for maintaining its health and appearance. To learn how to adjust your lawn mower’s cutting height for the best results, consult our expert guide on adjusting lawn mower cutting height.

Adjusting With A Hex Key Allen Wrench

The hex key Allen wrench is a standard tool that can be found in most garages, and is used to tighten screws and bolts.

To adjust the blade with a hex key Allen wrench:

Remove the battery cover from your mower if it has one, then remove the old blade using either a screwdriver or nut driver wrench as described above. Do not throw away these parts; you will need them later on.

Hold onto the metal part at the back of your new blade so that it doesn’t move while you’re working with it. 

Then place it over the axle spindle so that its teeth line up with those on your mower’s flywheel (or tines). Make sure none of these components are touching any other parts in their respective places nearby before proceeding further!

Insert one end of an Allen wrench under one side of each bolt head (where they connect together), then tighten this down until both sides are secured firmly together by hand – don’t use tools yet!

Adjusting With A Screwdriver And Nut Driver Wrench

Adjusting the blade with a screwdriver and nut driver wrench is one of the easiest ways to adjust lawn mower blades. 

It’s as simple as turning the nut in the direction of the arrow on your lawn mower blade, tightening it until it stops turning by hand, then backing off in quarter-turn increments until you can easily turn your blade by hand and have about 1/16th inch of space between each link. 

If you can’t turn your blade by hand at any point during this process, it’s too tight you’ll need to loosen it slightly before trying again!

If the handle on your Craftsman lawn mower is uncomfortable or at the wrong height, it can cause strain or pain during operation. Follow our simple steps in our guide on adjusting handle on Craftsman lawn mower to customize your mower’s handle to your specific needs for a more comfortable and enjoyable lawn mowing experience.

Adjusting While Lifting The Mower Deck With Jack Stands

If you want to perform this task while the mower deck is raised, you will need a floor jack and two jack stands. Make sure that the mower is secure with the jack stands before attempting to adjust the blades. 

Do not use a hydraulic jack or hydraulic stand to lift the deck of your lawnmower! In order for this method to work safely, the frame of your mower must be strong enough and balanced enough so that it can support itself fully while suspended by its own weight.

Tighten The Blade Bolts Securely

Use a torque wrench: Because the blade bolts are under tremendous pressure, you’ll want to make sure they’re tightened correctly. 

Using the correct size hex key or socket on your lawn mower is important because it ensures that you’re using just enough pressure on each bolt to ensure a tight fit without over-tightening it.


We hope that this guide has helped you understand how to adjust your lawn mower blades. It is important to take the time to make sure your blades are sharp and properly balanced so they do not cause damage when turning at a high speed. If you have any questions or concerns, don’t hesitate to reach out!

Further Reading

Types of Lawn Mower Blades: Learn about the different types of lawn mower blades, including standard, mulching, and high-lift blades, and how to choose the right one for your lawn.

How to Adjust the Blades on a Walk-Behind Mower: A comprehensive guide on how to adjust the blades on a walk-behind mower, including checking blade balance, sharpening blades, and testing for proper cutting height.

How to Change a Lawn Mower Blade: A step-by-step guide on how to change a lawn mower blade, including gathering necessary tools, removing the old blade, and installing the new one.


Can I sharpen my lawn mower blade at home?

Yes, you can sharpen your lawn mower blade at home with a sharpening tool, such as a file, grinder, or rotary tool. However, if your blade is severely damaged or dull, it may be best to replace it altogether.

How often should I sharpen my lawn mower blade?

Ideally, you should sharpen your lawn mower blade at least once a year, but it depends on how frequently you use your mower and the quality of your lawn. If you notice your lawn looks uneven or torn after mowing, it may be time to sharpen the blade.

How do I know which lawn mower blade to use?

The type of lawn mower blade you need depends on your lawn’s specific needs, such as the grass type, cutting height, and mulching preferences. Consult your mower’s manual or a professional for the best advice.

Can I switch out my lawn mower blade for a different one?

Yes, you can replace your lawn mower blade with a different type, brand, or size as long as it is compatible with your specific mower model. Be sure to consult an expert or the manufacturer’s instructions before making any changes.

How do I know when to replace my lawn mower blade?

You should replace your lawn mower blade when it becomes too dull, damaged, or worn to effectively cut your grass. Signs of a dull blade include ripped or torn grass, uneven patches, and a decreased cutting performance.