Lawn mowers: Blade sharpening made easy

Lawn mowers: sharpen the blades, but do it rightLawn mowers need care and maintenance to ensure they deliver the desired performance in the long term. In addition to regular cleaning and checking the drive, regular sharpening of the lawn mower blade plays a decisive role in mowing performance. This guide explains how to sharpen the blade.

Contents Why does the lawnmower blade need sharpening? How can I tell if the lawnmower blade needs sharpening? Instructions: Sharpening lawn mower blades yourself What protective clothing should I wear when sharpening? Questions and answers

Why does the lawn mower blade need to be sharpened? A sharp blade is essential for a precise cut. Frequent use and driving over sticks, stones and other small obstacles dulls the blade of the lawn mower over time. As a result, the blades of grass are no longer cut straight, but rather torn off and shredded.

How can I tell if the lawn mower blade needs sharpening? The cutting pattern is the best indicator to determine the need for sharpening. Blades of grass cut with a blunt blade look frayed. They dry out and the tips turn grey. If the lawn shows these signs, it is time to sharpen the lawn mower blade.

Instructions: Sharpening lawn mower blades yourselfIf you have some manual skills, you can sharpen the blade yourself and save yourself a trip to the specialist dealer or locksmith. The right equipment is important.

Tool listBalancing deviceInbus spannerOpen-end spanner without ratchetPipe wrenchAngle grinderScrewdriverVise

Gloved hands replacing the spark plug on a red lawnmower.

Step 1: Switch off the mower safelySafety has top priority. Make sure that the device cannot be started accidentally. This means: remove the spark plug connector from the petrol lawn mower, disconnect the electric lawn mower from the power supply or remove the battery from the cordless lawn mower. Also observe the applicable safety instructions of the respective manufacturer. This will minimise the risk of injury and allow you to safely remove the blade.

Man maintaining a lawnmower, tightening the blade with a wrench.

Step 2: Remove the lawn mower bladeBefore you start removing the blade, it is worth taking a look at the lawn mower operating instructions. It will explain how to remove the blade correctly. Otherwise, proceed as follows: Turn the lawn mower on its side so that you can easily access the rotor blade. Depending on the type of screw used, you may need one or more spanners or the help of a pipe spanner to loosen the blade from the engine mount. to prevent the petrol lawn mower from leaking oil, do not tip it completely on its side.

Rusty lawnmower blade on cardboard with abrasive discs and steel wool.

Step 3: Clean and check the bladeThe removed blade is now cleaned. Dirt and grass residue can be easily removed with a cloth. Next, you should check the lawn mower blade for damage. If the blade has been too badly damaged or bent by stones or similar foreign objects in the lawn, it makes sense to insert a new blade straight away.

Parkside angle grinder in use, with sparks flying from a metal piece in a vice.

Step 4: Sharpening the lawn mower bladeTo sharpen the blade, clamp it firmly in a vice. This ensures that the blade does not slip during sharpening. You can use an angle grinder with flap discs for sharpening. Grind the cutting edges recognisable at the ends of the knife one after the other by lightly running the angle grinder over the corresponding upper side. Make sure you maintain the original angle of the cut edge and do not remove too much material. If you do not have an angle grinder at your disposal, you can use a set of files. Although this is more time-consuming, it also produces a good result. Work from coarse to fine: start with a coarse file, remove old burrs and renew the cut edge. You can then round off the result with a finer file.

Hands sharpening a lawnmower blade on a workbench with tools.

Step 5: Balance the bladeGrind the blade so that the same amount of material is removed from both ends. Otherwise there will be an imbalance and the knife will become crooked. To check whether the blade is balanced, you can insert it through the centre hole onto a screwdriver held horizontally. If the ends of the knife remain level, the knife is balanced. However, if the blade tilts to one side, you will need to remove some material on that side. Otherwise, the resulting imbalance will damage the lawn mower's engine bearing later on during mowing. To achieve an even more precise result when balancing the lawn mower blade, a special balancing device can be used. This is available from specialised dealers.

Dirty lawnmower upside down, blade visible

Step 6: Installing the bladeOnce the blade has been sharpened and balanced, you can reinstall it. Make sure that you fit all the screws and washers in the right places. Only restart the lawn mower when it is standing on the ground and you are sure that all parts are firmly screwed in place.

What protective clothing should be worn when sharpening? Protective clothing should be worn when sharpening. This minimises the risk of injury and damage to health. The following are recommended as protection against the sharp blades and fine metal particles:GlovesBreathing maskSafety goggles

Questions and answers

How often a mower blade needs to be sharpened depends on how often it is used. Frequent mowing or a lawn that is particularly littered with stones and branches will cause the blade to become blunt more quickly. However, the lawn mower blade should always be sharpened once a season.

In general, any angle grinder can be used to sharpen the blade. However, it is important to use the right discs. It is best to use flap discs and not grinding discs. The latter are unsuitable for sharpening the cutting edges as they are coarser and quickly remove too much material.

A blade that shows clear nicks, cracks or chipping should be replaced. Otherwise, not only the cutting quality will suffer, but also safety.