How to Sharpen Lawn Mower Blades

Updated on March 10, 2018
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Angela loves researching new facts, especially those pertaining to science and history. She feels that knowledge is essential in growth.

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The most important thing to a green lush lawn is mowing with a well-sharpened lawn mower blade. The force needed to cut grass alone is enough to dull the blade, but often times a mower cuts more than grass, such as twigs, rocks, a stray toy hidden under a tree. This can leave the mower blade with dents as well as a dull edge. These dull edges will cause the tips of your grass to be unevenly chopped, which takes away from the fresh healthy look of the grass. At minimum, you should be sharpening them at least once a year. If you have a large lawn, you may need to sharpen them more frequently. You can tell you need to sharpen your blades by looking at the tip of a grass after it has been recently cut. If the tip is white, your blades are dull. If it is green, they are doing their job.

Tools Needed to Sharpen Mower Blades

  • Wrench
  • Protective gloves
  • Goggles
  • Clamp or block of wood
  • Sharpening tool (Mill bastard file with a vice to hold blade still or metal grinder)
  • Plastic mower blade balancer found at hardware store
  • Less than an hour of your time

How to Remove the Lawn Mower Blade

Safety First: The first and most important step when working with a lawn mower is to make sure the spark plug wire is disconnected. Place the spark plug away from the mower before dismantling the mower. You may also want to disconnect the battery. Although the chances that the mower will spontaneously start is unlikely, it is better to be safe than sorry.

When you decide to sharpen your lawn mower blades, wait until the gas tank is nearly empty. When you lean the mower on its side, there is less chance of gas spilling. Just in case, it is a good idea to use a tarp to protect the ground underneath when you tip your lawn mower over to get at the deck of the mower.

Removing the Blade: Removing the blade can be quite tricky; therefore, it is easiest if you use a clamp to grasp the blade, as you remove the bolt. A block of wood may work, although there is a higher chance that it will slip and you could hurt yourself than if you were to use a clamp. Once the blade is secure with the clamp, use a wrench to remove the bolt.

Sharpen Lawn Mower Blades

Assess the Damage: Once the blade is off, decide whether it is in good enough condition to sharpen or whether it needs to be replaced. Listed at the bottom of this article, there are guidelines that will help you decide whether it needs sharpened or replaced. If it is decided that the blade should be sharpened not replaced, you can begin sharpening.

Sharpen the Blade: There are several different tools you can use; a mill file or a grinding wheel will work the best.

If you choose to use a file... place the blade securely in a vice with one part of it overhanging the bench and with the cutting side face up. Begin filing from the middle to the tip. Do not sharpen in the opposite direction as this could cause uneven sharpening. Once one side is done, move the vice to have the other side facing outward and repeat with the same number of strokes you used on the first side. By using the same number of filing strokes this will eliminate any imbalancing.

If you choose to use a grinder... which is better for bigger nicks, hold the blade at a perpendicular angle to the grinder. Then grind in one direction along the length until you have a nice sharp edge. To keep it balanced, make sure to count your strokes; therefore, you can try to keep the same number of swipes with the grinder on both sides, to help with the balancing of the blade.

When sharpening the blade... make sure you go with the same angle that was on the blade prior to being sharpened. The factory bevel is the ideal angle at which will cut the nicest. Once the edge is nice and smooth without any pitting, then it is ready to be balanced and put back on the mower.

If you do not feel confident or do not have the tools, you can bring the blade to a mower shop where they can sharpen it on a grinder. Some may choose to bring the whole mower. Unfortunately, a mower shop may take longer get to get to it if you do not remove it before hand. By taking it off prior, they often will sharpen it while you are still in the store.

Test the Sharpness: Rule of thumb, if you can cut a piece of paper with the edge of the cutting tool, you can cut your grass well. So take a piece of paper and see if you can slice the paper in half without tearing it.

Underside of a lawn mower.
Underside of a lawn mower. | Source

How to Balance Lawn Mower Blades

Balance the Blade: This is an extremely important step and should not be ignored. In order for your mower to work, your blade must be balanced, otherwise your lawn mower will vibrate. If the vibrations are bad enough, it can ruin your entire mower, and you will have to replace the entire machine.

Plastic lawn mower balancers will only cost a few dollars at any home repair shop. If the blade is not balanced, then sharpen the heavier side until both sides are balanced.

Place Blade Back on Mower: Once the mower blade is balanced, it is time to place back on the mower. Place it back on with the washer, then tighten the bolt. Use the clamp to hold the blade still while you tighten. Reconnect spark plugs and battery, fill with gas, and you are ready to mow!

Know When a Lawn Mower Blade Replacement Is Necessary

There is a difference between dull, slightly chipped blades that need sharpening and ones that need to be replaced. Every time you go to sharpen your blades, you need to assess your blades to see if they are ready to be trashed.

Large Nicks: A nick here and there is okay, as long as it can be easily smoothed out during the sharpening process. On the other hand, once there is a nick or dent large enough that regular sharpening will not smooth away, the blade is damaged and should be replaced. With a nick or dent, this can cause the blade to become imbalanced. As stated earlier an imbalanced blade can ruin your lawn mower. Also, nicks that cannot be smoothed out, can increase in size as you mow.

Worn Blades: Once a blade has become so worn that you no longer can get a sharp edge with a grinder or file, the blade has become too old, and needs to be replaced. This may not be recognized with mere looking at the blade, but may become obvious as you try to sharpen it.

Making sure your mower blades are in great condition are key to having a great looking lawn. By doing this annually your lawn will be greener and your lawn mower will last many more seasons as a result!

Questions & Answers

    © 2012 Angela Michelle Schultz

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      • profile image

        Hendra 3 years ago

        Thank you, hopefully somebody discovers it helpful! http://exteriorwooddoorss.blogspot.com/

      • angela_michelle profile image
        Author

        Angela Michelle Schultz 5 years ago from United States

        Thanks for the great information. You are very passionate about them. I actually see them around sometimes. :) My husband likes his John Deere.

      • againsttheodds profile image

        againsttheodds 5 years ago

        Great article on DIY mower maintenance. If anyone does commercial mowing or even wants a GREAT mower for the property I would suggest Bob-Cat.

        Bob-Cat mowers come with the Extreme Discharge system design that is pretty much unmatched by any of the competition. Wider clipping dispersal means there is no longer a pile of cut grass to clean up. Surprisingly, bad dispersal is still a problem on some other brands of mowers, and it leads to an unsightly mess. The last thing one wants to do is clean up after mowing. The Extreme Discharge system is smooth in this regard. Effectively widening the "spray" by 30% than even the older generations of mowers. There are a series of adjustable anti-scalp rollers to keep the discharge component from scraping on areas that it should not. Up to 7 of these can be custom adjusted putting complete control in the hands of the commercial landscaper. One hand operation from a riding position makes it very simple to avoid obstacles and get closer cuts. When time is money then speed is key. The Bob-Cat mowers have everything needed for quick mowing operation.

        One part that probably will not need replacement any time soon is the excellent award winning seat. The lack of vibrations makes for a comfortable non-numbing mower ride. Vibration dampers in the ISO-ride system prevent bottom-outs and other jarring situations during mowing. The quick switch system allows for near instantaneous changing of deck height in order to allow for uninterrupted mowing. Zero-turn models of the new generation of mowers are on the cutting edge in terms of features. The Bob-Cat mower is created from design inception with ease of maintenance in mind. Everything is easily accessible from filters to belts. This is the perfect brand of mower for the DIYer who has even the smallest aptitude when it comes to tools. All parts can be found at the local dealer's place of business, and they can help with any further questions that you may have regarding Bob-Cat mower parts that you need to maintain.

      • angela_michelle profile image
        Author

        Angela Michelle Schultz 5 years ago from United States

        THanks so much Simone!

      • Simone Smith profile image

        Simone Haruko Smith 5 years ago from San Francisco

        Hahaa, I thought mowing lawn was as straightforward as just pushing a mower around and occasionally emptying the bag. Guess not! I'm glad you wrote this Hub.

      • angela_michelle profile image
        Author

        Angela Michelle Schultz 5 years ago from United States

        Thank you, hopefully someone finds it useful!

      • teaches12345 profile image

        Dianna Mendez 5 years ago

        Good one here for those who are getting ready for lawn care as summer approaches. Voted up!

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