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How to Safely Sharpen your Lawnmower Blade

Posted by Christine Crandall on Feb 28, 2019 12:41:30 PM

When advising people about lawn care, one of the most common pieces of advice is to sharpen your lawnmower blade. It is as if everyone knows how and when to do it, and little more is said. This is surprising because not only is a sharp blade vital to lawn health, but it can be a dangerous task if not done safely.

When to sharpen your lawnmower blade...

  • Prior to first mow of season
  • Any time you hit a rock
  • When grass cuts are ragged

Your lawnmower blade should be sharpened prior to your first mow in the growing season. This ensures crisp cuts that will prevent diseases from penetrating ragged edges. It will also prevent damaged ends, which can cause the grass tips to turn brown.

Generally speaking, your lawnmower blade will need sharpened a couple times throughout the season. You’ll need to increase the number based on how hard you are on the blade.


Removing the Blade

Safety comes first when doing any maintenance on an engine, but many people make the mistake of complacency when removing their lawnmower blade. Don’t make this mistake!

  • Remove the spark plug wire
  • Wear eye protection
  • Wear gloves

You begin the blade removal my unplugging the spark plug, so there is no way the motor can be started. Then, you must tip the mower straight back. If you tip it from side to side, gas and oil may leak out. (You don’t have to remove the gas and oil to remove the lawnmower blade!)

Once you tip the mower back, you should see two nuts holding the blade to the mower. Hold the blade with one hand and remove the nuts with a socket wrench. If you use something to stop the blade from moving, like a piece of wood, make sure you don’t bend the blade.

Tip: Make sure you use the right-sized socket, so you don’t ruin the bolt by rounding it with a loose socket.

How do I mow?

Just like that, the blade should be removed. Make sure you leave your lawnmower in a safe place while you sharpen the blade. Don’t leave it propped up if there are children nearby who could access it.

Sharpening the Blade

There are two primary goals when sharpening the blade: getting a good edge (while maintaining the angle) and removing all nicks. It is pretty basic, and there are multiple tools that can be used:

  • File
  • Drill
  • Grinder

1. Metal File: When a metal file is used to sharpen a lawnmower blade, it is best to place the blade in a vice to hold it still. This will allow you to concentrate on the angle instead of holding the blade. It will also allow you to apply the appropriate amount of pressure. Move the file in one direction, maintaining its current angle, until you have a sharp, nick-free edge.

2. Drill: Cordless drills with a sharpening stone attachment are a very easy way to sharpen blades. The attachments come with guards means to keep the blade at the right angle. When using motorized equipment to sharpen your lawnmower blade, eye protection is a must!

3. Grinder: Using a handheld or bench grinder is the typical shop owner’s preference. It makes very easy work of the sharpening. Again, make sure you wear eye protection and keep the blade at the correct angle.

Balance is Important

You want each side of your lawnmower blade to be balanced, and the sides can become unbalanced if more metal is removed from one side of the blade during sharpening. Check the balance of the blade before remounting.

Remounting the Blade

Cleaning the inside of the lawnmower is recommended before remounting the blade. Then, put it back on the bolt threads and tighten the nuts. You’ll have cleanly cut grass until it is time to sharpen your blade again!

If you would like a free lawn care estimate, get it from Greenfeet Lawncare!

Topics: mowing