How do I know when the blade needs sharpening or replacing?

    New lawnmower blades are an inexpensive way to cut down on your mowing time and improve the appearance of your lawn.


    Blunted blades can give your lawn a dull and uneven appearance and can lead to lawn diseases and unnecessary work for both you and your lawnmower. A dull blade could cause your mower to use up to 20% more fuel and considerably increase the amount of time you spend mowing.

    When the blades of grass start to appear ragged and brown after mowing, you should either sharpen or replace your lawnmower blades. How regularly you do this depends on what the blade comes into contact with; stones, twigs, paving edges and other landscape materials can cause damage to the blade edges, leaving them blunt.

    If the blade is bent, chipped, or damaged in some way, it is advisable to replace with a new blade rather than attempting to sharpen it. Damaged or bent blades will not cut effectively and could cause vibration and possibly damage your lawnmower.

    For information on sharpening your existing lawnmower blades, see below…

    How to Remove and Sharpen Your Lawnmower Blade

    Lawnmower Blade

    It is recommended to sharpen your lawnmower blade every 1-2 months if you mow your lawn regularly.

    First, disconnect your lawnmower from its power source and remove the spark plug wire to ensure that it doesn't start up accidentally and cause an injury. Always wear thick gloves and eye protection when removing the blade from a lawnmower.

    Using a wooden block to wedge the blade in place, remove the nut that fixes the lawnmower blade to the deck and carefully remove the blade. Don't hold the blade with your hand or foot during removal, as the blade is very sharp could potentially cause a serious injury.

    Use a bench grinder or a file to grind away any indentations or nicks, and smooth any rough edges. Try to file the blade as evenly as possible and to follow the original angle of the cutting edge. It is a good idea to file the same number of times on each side to in order keep each side even.

    Once sharpened, the lawnmower blade should "balance". This can be measured using a plastic balance tool or by hanging the blade through its centre hole on a nail driven into the wall. If one side is heavier than the other, file it down a little further until both sides are even.

    When re-applying the blade, remember that the sharp "cutting" side of the blade should be facing down, not up!

    Finding the right blades for your lawnmower

    It is usually quite simple to find the correct replacement blades for your lawnmower. Firstly you will need to determine the length of the blade, which is generally incorporated into the model number of the mower. This can usually be found on the top of the casing or near the motor. If you need more information on locating the model number, try our model number guide

    The most common size of lawnmower blade are 19" and 22". You will also need to determine the size of the shank, ie. the part of the motor shaft that the blade attaches to, in order to know the diameter of hole that you will need on your new blade.

    For help in locating the correct blade for your lawnmower, see our section on lawnmower blades