How to Sharpen Mower Blades with an Angle Grinder

I remember the first time I sharpened my own mower blade. It was a hot day in July. I looked at my lawn. It looked bad.

The grass was not green. It was brown at the tips. I looked closer. The grass was not cut clean. It was torn. It looked like someone chewed it.

My blade was dull.

I used to hate this job. I thought I needed expensive tools. I was wrong. I found a fast way. I use my angle grinder.

It changed how I work. I can now sharpen a blade in ten minutes. My lawn looks green again.

Here is how I sharpen mower blades with an angle grinder. It is easy and safe.

The Problem: Dull Blades Kill Grass

A dull blade does not cut. It tears the grass.

When the blade tears grass, the tip dies. It turns brown. This is why your lawn looks dull a day after you mow.

A torn tip is bad for the plant. It lets in sickness and bugs. A dull blade also hurts your mower. The engine has to work too hard. It wastes gas.

Signs You Need to Sharpen:

• Grass tips look brown or frayed.
• The mower engine sounds loud or tired.
• You have to mow the same spot twice.
• You hit a rock or big root.

I try to sharpen my blades two times a year. It helps a lot.

The Fix: My Easy Method

I use my DeWalt DCG413 angle grinder. You can use any grinder. Just make sure you can hold it well.

This job is loud. It makes dust. I do this in my driveway.

Step 1: Safety First

This is the most important step. Mower blades can hurt you.

Before I touch the blade, I pull the spark plug wire. I find the rubber boot on the front of the engine. I pull it off. I tuck it away.

If you skip this, the engine could start. That would be very bad.

Step 2: Tip the Mower

I tip the mower on its side. But be careful.

I always tip it with the air filter facing up.

If you tip it the other way, oil will spill. It will go into the air filter. I did this once. My mower smoked for an hour. Do not do that.

Step 3: Take Off the Blade

I use a piece of wood. A scrap 2×4 works well. I jam it between the blade and the mower deck.

This wood stops the blade from turning. Now I can turn the bolt.

I use a socket wrench. I turn the bolt to the left.

My Pro Tip: Before I take the blade off, I mark it. I use a marker. I write “This Side Down” on the bottom. It is easy to put a blade on wrong. If you do, it will not cut.

Step 4: Check the Blade

I wipe off the old grass. I look at the sharp edge.

• Small dents: I can fix these.
• Big cracks: If I see a crack, I stop. I throw the blade away. It is not safe.
• Thin metal: If the metal is very thin, I buy a new blade.

Step 5: Set Up the Grinder

I put the blade in a vise. I clamp it tight.

I use a 60-grit flap disc on my grinder.

Why I Use a Flap Disc: I used to use a hard stone wheel. It was too rough. It took off too much metal. It made the blade hot.

A flap disc is made of sandpaper layers. It is soft. It smooths the metal. It keeps the blade cool. It is easier to control.

Step 6: Grind the Edge

This is the fun part.

I look at the angle on the blade. It is usually about 30 degrees. I try to match that.

I hold the grinder steady. I move it along the blade.

• Long strokes: I move from the inside to the tip. One smooth line.
• Light touch: I do not push hard. I let the tool do the work.
• Watch the heat: If the metal turns blue, stop. Blue means it is too hot. Hot metal gets dull fast.
• Count passes: I count in my head. One, two, three… I usually do 10 passes.

I do the same thing on the other side. I try to do the same number of passes.

Note: You do not want a razor edge. A mower blade hits dirt and sticks. A razor edge is too weak. It will break. You want an edge like a butter knife. Sharp, but strong.

Step 7: The Balance Test

A sharp blade must be balanced. If one side is heavy, the blade will shake. This shaking can break your mower engine.

My Simple Test:

1. I put a nail in my wall.
2. I hang the blade on the nail by the center hole.
3. I watch it.

If the blade stays flat, it is good.

If one side dips down, that side is heavy.

I grind a little metal off the heavy side. I grind the back edge, not the sharp edge. I check it on the nail again. I do this until it hangs straight.

Step 8: Put It Back On

I put the blade back on the mower. I check my mark. I make sure the sharp side faces the grass.

I put the bolt back in. I tighten it with my hand first. Then I use the wood block again. It holds the blade. I tighten the bolt hard with my wrench.

I put the spark plug wire back on.

Why I Like the Angle Grinder

I have tried many ways to sharpen. The angle grinder is the best for me.

The Results

I started my mower. It ran smooth. It did not shake.

I cut a row of grass. The cut was clean. The grass was green. The brown look was gone.

It felt good to fix it myself. I saved money. I did not have to go to the shop.

FAQs – How to Sharpen Mower Blades with an Angle Grinder