A dull lawnmower blade doesn’t just make mowing harder.... did you know it can tear grass instead of cutting it? When your grass is torn, it leads to frayed, brown tips and a stressed-out lawn.
Whether you use a gas push mower, a riding mower, or a reel mower, sharpening the blades helps your equipment work better and your yard look cleaner. The steps are different for each type, but they all follow the same goal: remove buildup, smooth out the edges, and keep things balanced.
What You’ll Need
Not every mower uses the same tools, but here are the basics. You’ll only need a few of these depending on your setup:
- Safety glasses/eye protection
- Work gloves
- Socket wrench or adjustable wrench
- Bench vise or sturdy clamp
- Metal file/flat file
- Sharpening stone or rotary sharpening tool
- Angle grinder or bench grinder (optional)
- Blade balancer (or a nail in the wall)
- Reel mower sharpening compound kit (for reel blades)
- Stiff wire brush or putty knife
- Block of wood
- Cleaning rag
Sharpening a Push Mower Blade
A walk-behind mower is the most common, and their single, horizontal blade is easy to remove and sharpen.
1. Disconnect and Tip Safely
- Pull the spark plug wire on gas mowers. For electric mowers, remove any kind of key or kill switch. This prevents accidental starting.
- Tilt the mower on its side. Make sure to keep the air filter and carburetor facing up for gas mowers.
- Wedge a wooden block against the blade to stop it from spinning.
2. Remove the Dull Blade
- Use a socket wrench or adjustable wrench to loosen the center bolt. (Pssst. Some mowers have reverse-threaded blade bolts so don't rely on "lefty-loosey, righty-tighty")
- If you have a hard-to-loosen blade, add extra leverage or tap the wrench with a mallet.
- Snap a photo or mark the blade’s down-facing side before removal to reinstall it correctly.
3. Clean and Inspect
- Use a brush or scraper to remove caked-on grass and rust.
- Look for cracks, warping, or deep chips. If you see any, get a replacement blade.
4. Sharpen
You can use a metal file, sharpening stone, or angle grinder. And when we say sharp, we don't mean that you need to sharpen these like your chef's knives. Butter knife sharp is fine!
File method:
- Clamp the blade in a vise.
- Hold the file at the same bevel angle as the blade (usually around 45°).
- File from the inside out in one direction.
- Use even, smooth strokes.
- Do the same number of strokes on both ends.
Grinder method:
- Follow the blade’s beveled edge for the correct angle.
- Keep the tool moving at a consistent angle to avoid overheating.
- Use light passes until you get your desired blade sharpness—don’t overdo it.
5. Balance the Blade
- Hang the blade on a nail through the center hole.
- If one side dips, it’s heavier—file it down slightly until balanced (an unbalanced blade can be really wobbly).
6. Reinstall and Test
- Bolt the blade back on tightly.
- Reconnect the spark plug.
- Set the mower upright and you’re good to go.
Sharpening a Riding Mower Blade
Riding mowers are heavier and often have multiple sets of blades. The process is similar to push mowers but with a few key differences.
1. Safety First
- Turn off the engine, remove the key, and disconnect the spark plug.
- Engage the parking brake.
- If needed, remove the mower deck for easier access.
2. Access the Blades
- Lift the mower deck using ramps, a jack, or by removing it entirely.
- Use wood blocks or wheel chocks to prevent rolling.
- Clean off the deck underside.
3. Remove the Blades
- Use a wrench or impact driver to remove the mounting bolts.
- Mark the orientation of each blade so you reinstall them correctly.
- Wear gloves—these blades are larger and heavier.
4. Clean, Sharpen, and Balance
Same technique as with a push mower:
- Clamp each blade in a vise.
- Sharpen using a file, grinder, or sharpening stone.
- Keep the original angle of the blade edge and use smooth, even strokes.
- Balance each blade before reinstalling.
5. Reattach and Secure
- Tighten all bolts securely.
- Reinstall the mower deck if removed.
- Reconnect the spark plug, and start the engine to test.
Sharpening a Reel Mower Blade
Reel mowers work differently. Instead of one spinning blade, they use a cylinder of blades that spins against a fixed cutting bar. Sharpening these requires a different approach.
1. Clean the Mower
- Brush away grass clippings and dirt.
- Use a rag to wipe down the blades.
2. Use a Reel Sharpening Kit
These blade sharpener kits include sharpening compound and a hand crank.
- Apply compound to the cutting edges of the reel.
- Attach the handle to the reel gear and turn the reel backward.
- The blades grind against each other, sharpening blades gradually.
- Do this for several minutes.
- Wipe off excess compound when done.
3. Adjust Blade Contact
If the blades aren’t cutting cleanly after sharpening, you may need to adjust the tension between the reel and the bed knife (the fixed blade).
- Use the adjustment screws on the sides.
- Tighten until the reel blades just barely touch the bed knife.
FAQs
Do I need to remove the blades to sharpen them?
For push and riding mowers, yes—it gives better results and makes the job safer. For reel mowers, you sharpen the blades while they’re still attached.
How sharp should a mower blade be?
You don't need a super sharp edge, by rule of thumb it should feel like a butter knife—sharp enough to cut cleanly, but not razor sharp (a common mistake). Too-sharp blades dull faster and can chip more easily.
What happens if I skip sharpening?
You’ll get uneven cuts, brown grass tips, and a stressed lawn. The mower will also work harder and burn more fuel (or battery).
How can I tell when it’s time to sharpen?
- The grass looks frayed with ragged edges after mowing
- The mower feels like it’s dragging or pulling
- You hear more tearing than slicing
- You see dings, dents, or a blunt edge on the blade
