Sharp mower blades give grass a clean cut and cut down your mowing time. Blunt mower blades can not only cause your mower engine to strain but also damage your turfgrass. Keeping the mower blades sharp improves mower engine performance and running costs. Fortunately, you can sharpen your mower blades without detaching them from the mower.
To sharpen your lawnmower blades, wear protective gear and assemble the necessary tools. Disconnect the mower from its power source, cap the gas tank, and position the mower on its side. Sharpen the blades at the correct angle, wash off the debris and test the mower.
Signs of blunt lawn mower blades
Here are signs of blunt blades that require sharpening
Rugged cuts on cut grass
Blunt mower blades don’t deliver an even cut like sharp blades. Blunt blades leave the grass looking rough and uneven. Unlike blunt blades, sharp blades cut the grass at the same height. A rugged cut is a glaring sign that you need to sharpen your lawnmower blades
Jagged edges on cut grass
Jagged edges on the cut grass also point to blunt mower blades, as they cannot deliver a clean cut. Irrespective of the mower angle, sharp blades will deliver swift swipes that leave straight edges and a cleaner cut.
Grass color changes after mowing
Your turf browning after mowing the lawn is another sign that you’re using blunt mower blades. The rough cuts from blunt blades injure and stress the grass. As a result, turf health deteriorates, and the grass starts to lose color.
A lawn suffering from injury stress after cutting using dull mower blades recovers slowly and has lower natural defenses against pests and diseases. Therefore, if you notice pest infestation or disease invasion a few days after mowing your turf, check the condition of the mower blades.
You require more effort to finish mowing
If you have to make more passes to cut the grass to the correct height, it’s likely that the mower blades aren’t sharp enough. Dull mower blades may also force you to work longer than usual to complete mowing your yard. And if you’re putting more muscle into pushing your walk-behind mower, the blunt mower blades could be making the job more strenuous.
The mower disrupts grass and disturbs the soil
You can tell that your mower blades need sharpening if they’re pulling up grass chunks and topsoil instead of smoothly cutting the grass. Dull blades. This is common with thick or tall grass. The grass may wrap itself around the mower blades, forcing the blades to disrupt soil and pull up grass chunks.
The lawnmower stalls
Though not a common occurrence, blunt lawn mower blades can stall a lawnmower. Dull blades will collect a lot of debris. Consequently, small parts in the engine may not work as they should, leading to the engine stalling. The engine is forced to deliver more power, especially when working on lawn areas with dense turf grass, and may stall in the process.
Visible wear and tear
Finally, the most sure-fire sign of blunt mower blades is the blades’ state. If they have dents and nicks or appear bent at certain points, they obviously aren’t performing up to par and need to be sharpened or replaced.
Can you sharpen the lawn mower blade without taking it off?
The most convenient way to sharpen lawn mower blades is by accessing the cutting deck and removing the blades to work on them separately. However, you can still sharpen the blades without taking them out. You have to turn the mower on its side to gain access to the cutting blades.
When sharpening the mower blades without removing them, you risk the mower tipping over and hurting you since it’ll be positioned on its side. To prevent this, ensure you firmly secure the mower using wooden blocks or wedges.
Note: You use the same tools to sharpen blunt lawn mower blades even when you remove the blades.
How do you sharpen lawn mower blades without removing?
You can sharpen lawn mower blades without removing them. Here is a step-by-step procedure to follow:
Wear safety apparel
Handling lawn mower blades is a safety risk, especially after sharpening. Ensure you wear heavy-duty safety gloves before you start working on the mower blades.
Also, you’ll be using a metal grinder or file to sharpen the blades. The last thing you want is small metal particles or shrapnel flying into your eyes as you use these tools. Therefore, put on safety goggles before sharpening the lawnmower blades.
Assemble the necessary tools
Have all the required tools and materials in your workstation. The equipment you need to sharpen your mower blades includes:
- A grinder or flat file
- Steel wool
- A wire brush
- A 4×4 wooden block (12”-18”)
- A 2×4 wooden block (16”-20”)
- A de-burring rod
Disconnect the mower from power source
Depending on the type of mower, disconnect it from the power source before you start working on it. Disconnection may be unplugging the cord from the outlet on an electric mower or disconnecting the spark plug from the ignition wire.
Turn the lawn mower on its side
Place the mower on its side to access the mower blades. Note that a gas-powered lawnmower should only be turned on one side with the carburetor and air filter side facing up. Turning it the other way might cause oil leakage.
Place a block of wood underneath the motor for added stability.
Sharpen the blades
Secure the blades in position. You don’t want the blades to move back and forth as you’re working on them. Place a 2×4 wooden block above the cutting deck and another one under the blades to firmly secure them as you grind the cutting edge
Before sharpening, remove any debris stuck on the blades, such as grass shoots and dust particles. Use a wire brush or steel wool.
When sharpening the blades, position the file or electric grinder at a 45-degree angle for sharp blades that will deliver precise cuts. Also, ensure even strokes so the sharpness stays the same throughout the length of the cutting edges.
For the best results, we don’t recommend back and forth sawing motion when grinding down the cutting edges of your mower blades. Instead, apply a single forward stroke and lift the grinder to the original position to perform the same forward stroke again.
Meanwhile, if the mower blades have several nicks, sharpen them using a bench grinder. Finally, check whether the blades are well-balanced.
Don’t sharpen both sides of the mower blades. Like scissors, mower blades are designed to have only one sharpened edge. If you sharpen both edges, the blades will become blunt much quicker.
However, this doesn’t mean that you should ignore the underside edge of the mower blade. If it has nicks and other rough bits, use a de-burring rod to smoothen it without sharpening it.
Wash the Blades
Wash the mower blades after sharpening them to remove all the metal debris. Wait for the blades to dry or wipe in a unidirectional sweep with a cotton rug. Power up the mower.
Test whether the blades are now delivering a sharp, seamless cut.
- University of Maryland Extension: Dull Mower Blade/Mower Injury – Lawns
University of California- Integrated Pest Management Program: Dull Mower Blades