Changing your lawn mower blade requires a few basic tools, some safety precautions, and a bit of hands-on effort. By following my simple steps, you’ll complete this mower maintenance task at home with ease.
Dull, damaged blades tear grass rather than cut it cleanly, leaving the lawn ragged and exposing it to diseases, pests, and fungus. Most blades can be sharpened 5 to 10 times before replacement. You should also replace your mower blade if it is dented, chipped, really thin, riddled with holes, or bent.
Whether you have a push mower or a riding mower, this step-by-step guide will teach you everything you need to know and provide tips for troubleshooting any issues that may arise after replacement.
| Skill level: Beginner Estimated time: 30 to 60 minutes Cost: $15 to $60 for a replacement blade, or $30 to $100 total if you need to purchase additional tools, such as a socket wrench, fuel siphon, or torque wrench. |
What you’ll need
- New blade: Make sure it’s the right size and type for your mower. If in doubt, check your mower’s model number or bring the old blade with you to the store for reference.
- Socket wrench or ratchet: You’ll need this to loosen and tighten the blade bolt. Check your mower’s manual to find the correct socket size.
- Wire brush, scraper, or rug: Use these to clean grass and debris from the underside of the mower deck.
- WD-40 or similar lubricant: Handy if the blade bolt is stuck or rusted in place.
- Fuel siphon or empty fuel can: For gas-powered mowers.
- Block of wood or blade removal tool: Wedge this in place to stop the blade from spinning while you loosen or tighten the bolt.
- Work gloves: To protect your hands from the blade.
- Safety glasses: Optional, but a good idea to protect your eyes from debris.
- Torque wrench: This is a tool that lets you tighten bolts to a specific force. Optional but recommended to ensure the new blade is tightened to the correct specification.
Take precautions before you begin
Before proceeding with the blade replacement, make sure you’re working safely. You’ll be dealing with sharp edges, heavy equipment, and possibly fuel or electricity.
Start by disconnecting the power source. For gas mowers, pull the spark plug wire off the plug. For electric mowers, either unplug the cord or remove the battery.
If you’re working with a gas-powered push mower, empty the fuel tank or run it low before tipping the mower. A full tank can lead to gas or oil leaks when tilted, which could damage the engine. It’s best to use a manual siphon pump to do this.
Make sure the mower is cool before you begin. If you’ve recently used the mower, give it at least 30 minutes to cool down before you start. Then, move it to a flat, stable surface like a garage, driveway, or patio. You need the mower to be sitting level and steady while you loosen the bolts and handle the blades.
Finally, wear protective gear. Sturdy gloves will protect your hands from sharp blade edges and rusty bolts. Safety glasses are optional, but helpful for keeping dust, rust, or debris out of your eyes.
My tip: I’ve seen people siphon gas by mouth; don’t do that. It’s dangerous, toxic, and not worth the risk. Also, never tip the mower just to pour out the gas. It’s messy, unsafe, and can damage the engine or cause leaks.
Read more about lawn mower types and their maintenance in our guides:
- Best Lawn Mower Maintenance Practices
- How to Change Spark Plugs on a Lawn Mower
- How to Change Oil in a Lawn Mower
- 10 Best Lawn Mowers
- Lawn Mower Safety Tips
- Best Riding Lawn Mowers
- Electric vs. Gas Lawn Mowers
Step 1: Access the blade
The steps depend on whether you have a push mower or a riding mower, so follow the instructions for your type below:
For push mowers: Tip the mower on its side with the air filter and carburetor facing up. This helps prevent fuel or oil leaks. Stabilize the mower by wedging a block of wood or brick under the deck to keep it steady while you work.
For riding mowers: To access the blades, you need to elevate the mower deck to its highest position using the height adjustment lever. In some models, this gives enough access to the blades from underneath.
However, other models may need to remove the mower deck entirely. You need to lower your deck as much as possible. Then locate the drive belt running from the engine pulley to the mower deck pulleys. Release the belt tension. Carefully slide the belt off the engine pulley.
Most mower decks are connected to the frame with front hangers, rear stabilizer arms, and lift links. You need to unhook or remove them. Double-check that everything is disconnected and carefully slide the deck out from the side.
My tip: Keep your pins, washers, or clips you removed in a small container so nothing gets lost during reassembly.
Read more: 9 Best Lawn Mowers for Big Yards
Step 2: Remove the old blade
Before removing the blade, take a moment to look at how the old blade is positioned. The sharp edge typically faces the direction of rotation (clockwise), and many blades are marked with “this side down.” You can also mark the downward-facing side with a marker before removing it.
To remove your old blade from both types of mowers, use a blade removal tool to keep the blade from spinning while you work. If you don’t have one, you can wedge a 2×4-inch block of wood between the blade and the mower deck.
Next, use a socket wrench to turn the center bolt counterclockwise to loosen it. If the bolt is stuck, spray a generous amount of WD-40 or similar lubricant around the base of the bolt and let it sit for about 10 minutes to break down any rust or debris. After the wait, try loosening the bolt again. Once it comes free, carefully slide the blade off the shaft.
My tip: Take a photo of the old blade before removal to use as a reference during the installation process.
Read more: 9 Best Lawn Mowers Under $300
Step 3: Inspect your blade
Before anything else, take a look at the blade. If it’s simply dull but in good shape, sharpening is all that’s needed. Use a flat file, bench grinder, an angle grinder, or a sharpening attachment on a power drill to hone the edge. If the blade is chipped, bent, cracked, or worn down unevenly, it’s safer to replace it.
My tip: This is a great time to inspect and clean the underside of your mower deck. Use a wire brush, scraper, or rag to clean off grass clippings and debris. A clean deck improves airflow and cutting performance.
Read more: How Often Should You Sharpen Lawn Mower Blades?
Step 4: Install the new blade
When installing the new blade — whether on a push mower or riding mower — you need to position the blade correctly. You can refer to the photo you took before removal, the mark you made on the old blade, or check for the labeling on the blade itself. Many blades are marked with phrases like “This side down” or “grass side.” Be sure that the labeled side faces toward the ground when the blade is mounted.
Once the new blade is in place, insert the bolt and hand-tighten it to ensure it threads correctly. Then, secure the blade in place using the blade removal tool or the block of wood to prevent it from spinning, and use a socket wrench to tighten the bolt firmly.
If you have a torque wrench, check your mower’s manual for the recommended torque; most mowers are typically between 30 and 60 ft-lbs.
Important: Don’t over-tighten; you want it snug, not stripped.
Read more: 10 Best Lawn Mowers for Small Yards
Step 5: Final checks
For push mowers: Make sure the blade is secure, straight, and doesn’t wobble. Once you’re done, carefully tip the mower back onto all four wheels. Then, reconnect the spark plug wire or battery and start the mower briefly to make sure it runs smoothly and doesn’t make any unusual sounds or vibrations. If everything sounds and feels normal, you made it great.
For riding mowers: If you removed the deck, reconnect it by reversing your earlier steps. First, slide the deck back under the mower frame, then reconnect all the linkages, pins, and brackets in the same order they were removed. Reattach the belt to the engine pulley, ensuring it is properly aligned and tensioned. Once everything is reconnected, raise the deck to your preferred cutting height.
Read more: How Much Does a Lawn Mower Cost
Troubleshooting after blade replacement
Even after a successful blade replacement, you may encounter some unexpected issues. Small issues, such as vibration, uneven cuts, or starting trouble, are common but easy to fix. As the University of Illinois Extension notes, an unbalanced blade can create a slight wobble that causes strain on a mower and may result in an uneven cut.
Below is a list of common mower issues that can happen after changing the blade, along with their causes and solutions.
| Problem | Solution |
| The mower vibrates excessively. | Remove the blade and check the balance using a balancer or nail-on-the-wall trick. Re-torque the blade bolt to the manufacturer’s specification. Replace the blade if it’s bent or damaged. |
| Grass is cut unevenly or looks torn. | Remove the blade and reinstall with the sharp edge facing the grass. Inspect and replace the blade if needed. Ensure the blade sits flat against the spindle. |
| The mower won’t start after the blade change. | Check and reconnect the spark plug wire. Let the mower sit for 15 to 30 minutes, then try starting again. Recheck blade installation and orientation. |
| Loud noise or clunking sound. | Re-torque the blade bolt. |
| The mower cuts too low or scalps the lawn. | Confirm correct blade orientation. Verify that you are using the correct replacement blade for your model. |
| The blade won’t come off during change. | Spray with penetrating oil (e.g., WD-40) and let it sit for 15 minutes. Then, retry with firm, steady pressure. |
Read more: How to repair a lawn mower
FAQs about changing the mower blade
Replace the blade if you see chips, cracks, or warping, or if the grass looks torn or uneven after mowing. If you’ve sharpened it multiple times and it still performs poorly, it’s time to replace the blade.
You need to clean the blade after each use, avoid mowing over rocks or hard debris, and sharpen it after 25 to 50 hours of use or at least once per season.
To determine if your blade is balanced, hang it from a nail through the center hole, or use a blade balancer. If one side dips lower, it’s unbalanced and needs to be filed down evenly.
If you put the mower blade upside down, your mower will cut poorly or not at all. You need to flip it and reinstall it correctly so the cutting edge faces downward and the curved edge points up toward the mower deck.
Yes, as long as your mower is compatible. Mulching blades chop grass into finer clippings but may require a mulching plug kit to work properly.
Read more: What is a Mulching Lawn Mower and How Does It Work?
Find a professional near you
Changing your lawn mower blade is a simple task, but it does take time, patience, and the right tools. If you’d rather skip the maintenance tasks, consider contacting a lawn care professional. They can handle everything from mowing and yard cleanup to pest control, so your yard stays healthy and looking its best.
Main Photo Credit: Photo by Michelle Selzer
Sources:
“Lawn Mower Maintenance,” Colorado State University Extension.
“Mower Maintenance,” University of Illinois Extension.
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