How to Sharpen Your Lawn Mower Blades in Under an Hour

Ben Kissam
Written by Ben Kissam
Updated April 12, 2022
Woman mowing lawn in front of her house
Photo: DusanManic / E+ / Getty Images
Difficulty

Simple

Saturday skill builder.

Time to complete

1 hour

Cost

$20 to $40

Save some cash and sharpen (or file) by hand

What you'll need:

TOOLS

  • Blocks or a workbench (if possible)
  • Large file or sharpening stone
  • Electric angle grinder (optional)
  • Gloves
  • A long sleeve t-shirt
  • Eye protection
  • Vise
  • Socket wrench
  • Scraper tool
  • Bowl
  • Rag

SUPPLIES

  • Bleach and water

The sweet smell of spring is here, and with it comes some tasks to check off the old to-do list. Among those projects, getting your lawn mower spring-ready is a simple task that'll pay off all summer and fall.

It's pretty simple: Sharp lawn mower blades are not only more effective, but safer, too—not unlike how a chef will tell you that sharpened knives are actually much safer than dull ones. In this guide, learn two different ways to sharpen lawn mower blades safely. It only takes about an hour!.

  1. Assess Your Blades

    Cleaning lawn mower blade with a brush
    Photo: aigarsr / Adobe Stock

    Look at your lawn mower blades. Do they look worn or dull? Are there noticeable dents, possibly from running over stones or an object? In certain instances, a lawnmower blade can be too far gone, and may warrant replacement.

    If it's cutting grass unevenly or you only see minor dents and nicks, you can likely sharpen it and preserve the life of your blade.

    You should sharpen a lawn mower every 25 hours you spend cutting. Estimate how long it takes to cut your lawn, then divide 25 by that number to figure out roughly how many mows you can get out of each sharpening.

  2. Hoist the Lawnmower on Blocks, If Possible

    Removing spark plug on a lawn mower
    Photo: Александр Овсянников / Adobe Stock

    First, remove the spark plug from your lawnmower. This prevents any possibility of it turning on accidentally while you work. Locate the spark plug cap on the side of the engine. (By the way, replacing your spark plug is one of 11 important lawn mower maintenance tips you should keep in mind before the summer heat rolls through.)

    Ideally, set up on a workbench or blocks high enough to keep you from sitting on the ground. If not, place your mower somewhere you'll be able to work comfortably.

    Whether from the floor or blocks, pull your lawnmower straight back (bring the handle towards you so the undercarriage sits face up). Don't tip it on its side, or oil and gas can leak into it.

  3. Remove Your Blade, Then Clean and Inspect

    Handyman removing lawn mower blade with a wrench
    Photo: Maksym Povozniuk / Adobe Stock

    Remove grass and any other debris built up on your lawn mower's blade. Use a socket wrench to remove the blade. Be sure to carefully size your socket wrench prior to turning the nut. Your blade is (or at least should be) secured tightly; too much force with the wrong size bit can strip the nut and make it difficult to remove.

    Use a small scraper tool or steel brush to carefully remove any other caked-on debris or dirt. Mix one part bleach to every nine parts water (a small bucket with a splash of bleach will do), and clean your blade with a rag. Dry it off before sharpening.

  4. Securely Clamp Your Mower's Blade Into a Vise

    Clamp your blade into a vise with one half of the blade sitting above the clamp at a 45-degree angle. Make sure it's secure, but don't tighten it so much that you create additional dents or damage. You'll sharpen one side at a time.

  5. Sharpen Your Blade

    Sharpening lawn mower blade by hand
    Photo: BanksPhotos / E+ / Getty Images

    There are two popular methods for sharpening your blade: by hand and with a machine.

    Sharpen Your Mower Blade By Hand

    The simplest way to sharpen your blade—and most affordable if you're planning to invest in tools that'll make your lawn equipment last a lifetime—is to sharpen it by hand. A large sharpening file costs about $20 at your local home improvement store and will do the trick nicely. 

    Run the sharpening file along both edges of the blade on either side. File from the inside of the blade outward. 

    Sharpen Your Mower Blade With Machine

    The other option is to use an angle grinder. This costs between $40 and $60 at home improvement stores and run on electricity or rechargeable batteries.

    Always wear ear and eye protection when working with an angle grinder. With the blade clamped into the vice, run the angle grinder along both edges and sides of the blade. 

    Keep in mind: There are other ways to mechanically sharpen a lawn mower blade. One example is to use a drill-powered sharpening stone.

  6. Don't Oversharpen Your Blade

    There's a point of diminishing returns with sharpening a lawn mower blade. If it gets too sharp, the edge will become fine and your mower's blade will wear out sooner rather than later due to wear and tear. You'll also get less total sharpens out of the blade, which will warrant a quicker replacement. 

    With the hand sharpening method, go over each section of the blade two or three times. With an angle grinder, go over it once and inspect before doing it again. Don't press too hard with the device to avoid wearing it down.

Sharpening Lawn Mower Blades DIY vs. Hiring a Pro

If you have at least a sharpening filter on hand, this project is definitely a job most homeowners can tackle themselves. Getting blades sharpened by a professional will cost $5 to $20 per blade, perhaps more if damaged or excessively dirty.

You can likely outsource the job and save a few dollars by hiring a trusted local handyperson instead of going to a local lawn mower repair shop.