If the blades of grass appear frayed after mowing, the blades are blunt. It's high time to sharpen the lawnmower blade. With a little manual skill you can do this work yourself. The following instructions explain step-by-step how to do it.
How can I sharpen a lawnmower blade myself?
To sharpen a lawnmower blade, first remove the blade, fix it in the vice, sharpen it with a file and finish the edge with a sharpening stone. Pay attention to the correct sharpening side and balance of the knife before reinstalling.
Safety is key – this preparation is what counts
Work safety is the top priority when you sharpen a lawnmower blade yourself. It must be ensured that the mower cannot start to operate. You should exercise this caution when carrying out all work relating to the maintenance of a lawnmower. Here's how to do it:
- Pull the spark plug connector on the gasoline-powered mower
- Pull the cable out of the power plug on the electric lawnmower
- Removing the battery from a cordless mower
In addition, robust work gloves and protective clothing are mandatory. Ideally, you should wear long-sleeved clothing, long trousers, sturdy shoes and safety glasses.
Material and tool requirements
If all the work materials and tools are ready to hand, sharpening the lawnmower blades can be done quickly. This is how you should be equipped:
- Open-end wrench or adjustable wrench
- Allen key
- Pipe wrench
- Workshop quality file
- Whetstone, e.g. B. Scythe whetstone
- Vice
- rubber hammer
- Lawnmower instruction manual
How to remove the lawn mower blade
Turn the mower over so you can get to the lawnmower blade. Position a petrol mower so that the air filter is at the highest point. This way, on most models, gasoline will not leak from the tank. Now take the operating instructions for the lawnmower to hand in order to then remove the knife bar.
If the operating instructions are lost, this does not prevent you from continuing the work. Use the ring or open-end wrench to loosen the retaining screw in the middle. Make sure you memorize the location of any washers.
Tip
A petrol lawn mower blade should never be sharpened while installed. The risk of flying sparks igniting spilled gasoline is far too great. It is safer to remove the cutter bar so that it can be sharpened at a distance from the mower.
Manual sharpening tops the grinder - here's how it works
The removed lawnmower blade is fixed in a vice, which simplifies all subsequent work steps. Follow these steps:
- Use the file to sand the lawnmower blade from the outside to the inside
- In the second stage, rework the knife edge with the whetstone
- Remove the remaining burr completely so that it doesn't fold over later and the knife becomes dull again
Experts advise against sharpening a lawn mower blade with a flex. The knife is heated excessively, which results in a coarse grinding result. In addition, the removal increases unnecessarily, which can cause greater imbalance. This will only be corrected by removing the appropriate material on the other side.
What to do if you sanded from the wrong side?
In the heat of the moment, inexperienced hobby gardeners sometimes grind a lawnmower blade from the wrong side. If the quality of the lawn suffers as a result, the knife should be sharpened immediately. Unfortunately, this comes at the expense of a relatively large amount of material on the blade.
As long as the cutting quality of the grass is acceptable, the lawnmower blade will be gradually processed from the correct side with each subsequent grinding. In this way, the correct cutting angle gradually moves to the desired side. Here the angle should first be set a little flatter, as long as both sides of the knife are still sharp. If the bevel on the wrong side has disappeared due to wear, increase the angle on the correct side again.
Preventing lawnmower blades from being unbalanced – how to do it
If you do not grind a lawn mower blade to the same extent on both sides, the cutter bar will later swing back and forth more or less uncontrollably due to an imbalance in the mower. Here's how to prevent this situation:
- Drive a nail horizontally into a sturdy piece of wood
- Hang the knife bar at its center hole
- If one side tips down, there is an imbalance
- Sand the heavier side of the lawnmower blade again
Ideally, you can use this method to check the balance on the lawn mower blade between and at the end of the grinding work. Only when the cutter bar is perfectly balanced is it reinstalled into the mower. Otherwise, the engine block could be damaged and a simple grinding will result in an extensive lawn mower repair.
How often should lawnmower blades be sharpened?
The level of use largely determines how often a lawn mower blade needs to be sharpened. If the knives often hit branches and stones, they become dull more quickly. As a rule, sanding once per season is enough to mow a lawn perfectly. If you take a regular look at the lawnmower blade, you don't have to worry about frayed grass.
Tips & Tricks
To grow a perfect English lawn, a cylinder mower is essential. Unfortunately, its design defies any attempt to sharpen the knives manually. Special grinding machines for cylinder mowers, however, cost more than 2,000 euros, meaning that such an investment will only pay off in the 2nd or 3rd period at the earliest. Gardener generation amortized.
