How to Change a Lawn Mower Blade?

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After using a lawn mower for a while the blades can begin to wear out. With time they need to be changed or sharpened. There are instances when sharpening the blade won’t be enough to get it back to its original state.

Once you notice that your blades no longer cut grass as effective as they ought to, or you begin to notice small patches of grass in areas just mowed, then it’s time to change the blades.

Sometimes it would almost feel that the engine is over-laboring itself to cut grass it normally shouldn’t have a problem with.

Luckily, changing the mower blades is an easy process if you are willing to pay attention to the procedures outlined here. It should take less than half an hour to completely change the old blades to new ones if you are equipped with the right tools.

Changing the Lawn Mower Blades

Lift up the deck to expose the blades

Before lifting the mower to expose the deck that houses the blade be sure to drain out the oil from the carburetor to ensure you don’t spill them on the ground. If draining out the oil is not feasible for you, make sure the locks are properly secured before you start the process of taking out the blade.

Tilt the mower slowly up the side and use a hedge to support it. This should reveal the blade beneath. Consult your owner’s manual for necessary directions.

We highly recommend that you wait till the gas in the lawn mower is used up before attempting to change the blade.

Unplug the Spark Plug

Unplug the Spark Plug

It’s best practice to unplug the spark plug while attempting to change the blade of your lawn mower. It’s a safety precaution that can prevent electric flares in case oil or gasoline comes in contact with the spark plug. Unplugging the spark plug is not an important step if you hold the mower in a proper position; however, it’s an important precautionary measure.

What directions do you need to turn the nut to change a mower blade?

For most new models, the mower blade is held in place by a threaded bolt that screws the mower to the shaft of the engine. When the time comes to sharpen or replace the blades because of wear and tear you must turn the blade retaining bolts counterclockwise to get the old blade out of the engine’s driveshaft.

Turn it to the left: During mowing operation, the blades of most walk-behind mowers rotate clockwise to the right and if you must remove the blade you must turn the blade retaining bolt to the left (anticlockwise). Have a socket wrench handy, the wrench must be of appropriate size and fit on the bolt.

As you remove the blade, pay attention to the positioning of the blade and the degree of orientation it has because you will need them to reassemble a new blade.

You will have to mount the new Blade with the same orientation as the one you removed. Each mower model is specified with the orientation of the blade so it is a wise decision to consult your manual.

Installing a new Blade

First-and-foremost purchase replacement blades

It’s a wise idea to purchase replacement blades from the store or outlet in which you bought the land mower. They will have specific blades for the mower model you bought or at least give you directions on the right place to buy.

Most home improvement stores feature pre-weighted sharpened blades that you can buy directly.

Newer lawn mowers feature a single long blade that almost looks like a ruler. This kind is easier to fix via the blade retaining bolt onto the engine’s drive shaft.

The older models have a cap-like structure beneath in which two shorter blades can be attached.

You should talk to a hardware specialist on the specific kind of blade that is suitable for your lawnmower. Have the model number handy.

Unless your blades have been badly damaged you can salvage the old blades by sharpening them but if they have been worn out with chips or chunks within the metal it is best to buy replacement blades.

Mounting the new blades

Mounting the new blades

Using new washers and nuts of appropriate size line up the replacement blades in the proper position. Consult the owner’s manual to find out the directions for torque specs needed to tighten the nuts. If you can’t find it in the manual ensure you don’t over tighten the nuts as this can cause unwanted vibrations in the mower.


  • Be sure you have the same length of Blade as the old one before mounting.
  • Tighten the new blades to the deck carefully avoiding using too much force.
  • Read the owner’s manual for directions on torque force
  • Read the owner’s manual for directions on torque force
  • Use your hand, hedge or a tiny wood to stop the blade from turning during the mounting.

Check the blade

Once you have mounted the new blades check to make sure you have done the appropriate thing before starting up the lawnmower. Make sure it has no wobble while you move it up or down and it has been secured firmly to the engine’s drive shaft. Before switching on the lawnmower ensure you have filled it up with gasoline.  Wait for about an hour for proper circulation of fuel before switching it on.

Finally, check the air filter to be sure it is not dusty or clogged. Recheck the spark plug to ensure it is in optimum condition before replacing it in its port. After you have done a quick inspection you can now safely switch on the mower.

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