How to sharpen your lawn mower's blades
Lawn mowers need care and maintenance to ensure they deliver the best performance. In addition to regular cleaning, regular sharpening of the lawn mower blade plays an important role in mowing performance. This guide explains how to sharpen the blade.
Why does my lawn mower's 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 your lawn shows these signs, it is time to sharpen your lawn mower's blade.
How to sharpen your lawn mower's blades yourself
If you've got DIY skills, you can sharpen the blade yourself and save yourself a trip to the specialist dealer or locksmith. But the right equipment is important.
Tool list:
- Balancing device
- Inbus spanner
- Open-end spanner without ratchet
- Pipe wrench
- Angle grinder
- ScrewdriverVise
Step 1: Switch off the mower safely.
Safety has top priority. Make sure that the device cannot be started accidentally. This means removing the spark plug connector from the petrol lawn mower, disconnecting the electric lawn mower from the power supply or removing the battery from the cordless lawn mower. Also make sure you follow the safety instructions from the product's manufacturer. This will minimise the risk of injury and allow you to remove the blade safely.
Step 2: Remove the lawn mower blade.
Before 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: After ensuring the lawn mower is disconnected from its power supply, turn it on its side* so that you can easily access the 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 or petrol, do not tip it completely on its side. Follow the manufacturer's instructions on how to remove the blade safely.
Step 3: Clean and check the blade.
The removed blade can now be 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 hard objects on the lawn, it makes sense to insert a new blade straight away.
Step 4: Sharpening the lawn mower blade.
To 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 one after the other by lightly running the angle grinder over the 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. Work from coarse to fine. Start with a coarse file to remove the rough edges first. You can then round off the result with a finer file to renew the cutting edge.
Step 5: Balance the blade
Grind the blade so that the same amount of material is removed from both ends to avoid an imbalance and the sharp edge becoming 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.
Step 6: Installing the blade
Once 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 start the lawn mower again 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:
- Gloves
- Breathing mask
- Safety 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.
