Sharpening lawn mower cutting blades

To maintain the clean cutting pattern of your lawn mower, you should inspect your mower yourself or have it inspected at least once a year and then, if necessary, have the lawn mower cutting blades resharpened and thereby sharpened.

How do I recognize a blunt cutting blade?

So-called sickle mowers cut the grass in a horizontally rotating flapping motion. You can easily tell if the blades are still sharp enough by looking at the cut surface of each blade of grass, as dull cutting blades make the cut surfaces appear “frayed,” i.e., uncleanly cut. If this is the case, it is advisable to sharpen or change the lawn mower cutting blades. You can obtain these from specialist dealers as lawn mower replacement blades from all common manufacturers.

Observe safety instructions

Important: When sharpening or changing the cutting blade, please be sure to follow the manufacturer’s safety and warning instructions and always turn off your lawn mower completely! Disconnect the ignition on gasoline mowers, disconnect electric lawn mowers from the power supply and remove the battery from cordless lawn mowers beforehand. More detailed instructions for loosening and removing the cutting blade can usually be found in the operating instructions for your machine.

What tools do I need for installation and removal?

To be able to remove the cutting blade of your mower, you usually need some tools, which we would like to list below. Depending on the lawn mower model, you will need different pliers or wrenches.

Allen wrench

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This tool should not be missing in any workshop. The longer the Allen key is, the better, as great leverage is an advantage here.

Open-end wrench set / open-end wrench

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Every DIYer has such a wrench set in his workshop. Alternatively, a roller fork wrench can also be used. Even safer than open-end wrenches are so-called ring wrenches, which prevent slipping and thus injuries to the knife.

Pliers wrench / pipe wrench

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It can also be useful to use a pliers wrench or a pipe wrench. Especially with larger, very tightly fitting screws, you can reach your goal faster.

Soft-face hammer / Rubber mallet

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Sometimes it may be necessary to use a soft-face hammer. Its advantage over a standard rubber mallet is the reduced recoil. Some models offer movable lead elements in the hammer head, which further reduce the recoil.

Tools for sharpening the knife

Now we come to the sharpening of the lawn mower blade. Please always wear gloves for this, otherwise you could seriously injure yourself on the supposedly dull blade. We recommend the following tools for this step:

Workshop file

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There are some good manufacturers of high quality workshop files. By using a file, sharpening can be done more accurately than, for example, with a coarse flex.

Sharpening file / scythe whetstone

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A grinding file or scythe whetstone is ideal for the final fine grinding. The grain size may be somewhat coarser.

Tips and tricks for sharpening

Depending on the condition of the lawn mower blade, a different amount of metal must be removed during sharpening. Stones or sticks may have caused deeper indentations on the blade. It is important to note that the blade is ground and sharpened evenly to avoid imbalance.

Even though a flex would make the job much easier, you should refrain from doing so, as it is rather difficult to work accurately with such machines. It is best to pre-process the blades with the workshop file and then remove coarse burrs with the grindstone in the final step. Take special care to grind a fine secondary bevel at the tip of the blade to stabilize the blade or cutting edge.

You can then reattach the cutting blade to the lawn mower. Follow the reverse procedure here and make sure the blade has been inserted correctly to avoid loosening the next time you mow.



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