How to Change a Lawn Mower Blade



After a certain amount of time of using a lawn mower, the blades will need to be changed.  Due to the cutting and of the grass and mowing over the occasional rock, the blades will begin to dull and to chip.  This leads to blades that do not cut grass well anymore and the only way to fix this is to switch the blades with some sharp ones.  A person will know when the blades are dull when either the engine sounds like it is working harder than usual to mow the grass. A person can also tell if blades are dull if there are patches or lines of grass in areas that have just been mowed. 

Changing lawn mower blades is a simple procedure that will take less than half an hour if the right tools are already owned.  

The tools needed are in the second picture.
From left to right: 
Sharp blades (see note), work gloves, ratchet and socket or a wrench (see note)

Sharp blades are not needed.  If there is no spare sharp set of blades the time to change the blades will increase significantly because time will need to be added in order to sharpen the dull blades once they are taken off. 

The ratchet and socket will be easier to work with than a wrench, but a wrench will work in the absence of a ratchet and socket.

Step 1: Finding a Place to Change the Blades

Finding a proper place to change the blades can make the process easier.  For example, in the mower pictured in the first picture, the deck raises from the front.  In order to give more space the mower was driven to the top of a raised piece of ground to give even more room while working. 

Depending on the type of mower being used, different places will be better than others.  For example, a small push mower can just be flipped on its side on top of a cement pad after the oil and gas has been drained. 

For a mower parked on top of a raised piece of ground it is mandatory to use the parking break. 

1.  Find a place to park. 

2.  Switch the parking brake to the "On" position as seen in the second picture.

3.  Turn the engine off and let the mower cool if it is hot.   

4.  Place a block in front of and behind a tire as seen in the third picture. 
WARNING: If steps 2 and 3 are not followed the mower could roll down hill and cause injury.


Step 2: Find What Size Tool Is Needed

To find what size tools are needed you can either look it up in the users manual for the mower or the internet if tools need to be bought.  If the proper tools are on hand and only the proper size is left to be determined, it is easiest to put the socket or wrench onto the bolt to find the proper size.  It is recommended that when crawling under the deck of the lawn mower to place an old rug or sheets down to protect against minor scrapes and scratches as seen in the picture.

1.  Place the socket onto the ratchet as seen in the third picture. 

2.  Crawl under the deck and put the socket and wrench onto the bolt like in the fourth
     picture.  If the socket does not fit onto the bolt try a bigger sized socket.  If the socket fits
     onto the bolt but does not catch when turned, try a smaller sized socket.  When the
     socket fits snugly onto the bolt, the right socket has been found.

Step 3: Taking Off the Blade

Taking off the blade is a simple and quick process.  It is important to wear gloves while doing this to protect your hands from getting cut.  Wearing gloves will also protect your hands from getting grease on them. 

1.  Once the right socket is found, turn the ratchet's switch to the right as seen in the  
     second picture. 

2.  Place the ratchet and socket on the bolt and grab the the blade with the other hand as
     seen in third picture. 

3.  Twist the ratchet counterclockwise to loosen the bolt.  Once the bolt is loose enough,
     loosen the bolt by hand, continuing to turn counterclockwise as seen in the fourth

4.  Skip this step if there is only one blade. 
     Crawl out from under the lawn mower deck and place the pieces in a safe location
     where they will not be lost as seen in the fifth picture.  Repeat steps 2 and 3 again
     until all the blades are off.

Step 4: Switching the Blades

Once done taking the blades off, the next step is to switch the dull blades with the sharp blades.  If there are no sharp blades on hand, the dull blades will need to be sharpened. 

CAUTION:  Some lawnmowers that have more than one blade will sometimes have blades of different lengths.  Pay careful attention to make sure the spare blade is the same length as the blade it is replacing. 

1.  When done taking the blades off, crawl out from under the lawn mower deck and place
     the blades onto a cement or gravel surface as seen in the first picture. 

2.  Take the blade off as seen in the second picture

3.  Put the new blade on, making sure that the side with the long edge is facing the sky
     as seen in the third picture.  A way to check to make sure the blade is oriented correctly 
     is to have the sharp edges be doing the cutting if the blade turns in a clockwise 
     motion while looking at it from the top, like as seen in picture one.

4.  Repeat steps 2 and 3 until all the blades are changed. 

Step 5: Putting the Blades Back On

After replacing the dull blades with sharp ones, the next step is to place the blades back onto the mower. 

CAUTION:  Because some blades are different lengths, when putting the blades on, make sure to place the same length blade where it was originally at.

1.  Crawl under the lawn mower deck with the correct length blade and insert the bolt       
     into the hole (first picture) as seen in the second picture.

2.  Hand tighten the bolt clockwise.  Once the screw is hand tightened you will need to
     use the ratchet or wrench.

3.  Flip the ratchet switch to the left as seen in the third picture. 

4.  Place the socket onto the bolt and grab the blade with your free hand and turn
     counter clockwise until you can no longer turn the ratchet as seen in picture four.

5.  Repeat steps 1, 2, and 4 if there are addition blades to be put on.  

6.  Turn the mower blades in a circle a few times to make sure the blades do not
     catch each other.  If they catch, the proper length blades were not installed and the
     blades will need to be with ones of the correct length until the blades can freely turn. 

Step 6: Clean Up

After the blades are switched, all that is left is to clean up the small mess.

1.  Crawl out from under the deck of the lawn mower.

2.  Pick up the blanket or rug if one was used.

3.  Place tools back into the tool box or tool chest.

4.  Remove the blocks from the tire as seen in picture one.

5.  Turn the parking brake to the off position.  The off position for the parking brake can be
     seen in picture two. 

Step 7:



    • Classroom Science Contest

      Classroom Science Contest
    • Backyard Contest

      Backyard Contest
    • Sensors Contest

      Sensors Contest