Lawn Mower Blade Replacement | Complete Guide
Dull blades tear grass instead of cutting it. The result? Brown tips, stressed turf and a lawn that looks rough even right after mowing. Blade replacement takes 15 minutes and makes a huge difference.
Table of Contents
- When to Replace
- Blade Types
- Tools Needed
- Step-by-Step Replacement
- Part Numbers by Brand
- Sharpening vs Replacing
When to Replace
Signs You Need New Blades
Uneven cut - Some areas shorter than others. Blade may be bent or worn unevenly.
Torn grass tips - Brown edges on grass blades indicate tearing not cutting. Dull blade.
Excessive vibration - Bent or unbalanced blade causes shaking.
Visible damage - Nicks, gouges or chunks missing from cutting edge.
Won’t hold an edge - Blade dulls quickly after sharpening. Metal is work-hardened.
Thin blade - Worn beyond safe thickness. Less than 50% original.
[NEED REAL IMAGE: Dull blade damage on grass]
Replacement Schedule
- Light use (weekly) - Replace yearly or sharpen 2-3 times per season
- Heavy use (commercial) - Replace every 2-3 months
- After hitting objects - Inspect immediately, replace if damaged
Blade Types
Standard Blades
Flat blades with a cutting edge on each end. Work for most conditions.
- Best for: General mowing, side discharge
- Airflow: Moderate lift
- Mulching: Okay but not ideal
High-Lift Blades
Curved ends create more airflow to lift grass for bagging.
- Best for: Bagging clippings
- Airflow: Maximum lift
- Mulching: Poor (clippings blow out)
Mulching Blades
Curved or serrated design keeps clippings in the deck longer.
- Best for: Mulching mode
- Airflow: Recirculating
- Bagging: Works but less efficient
Gator/Toothed Blades
Serrated edges chop clippings into smaller pieces.
- Best for: Heavy mulching, leaves
- Airflow: Good recirculation
- Bagging: Not recommended
[NEED REAL IMAGE: Different lawn mower blade types]
Tools Needed
- Socket wrench (most blades use 15/16” or 5/8” bolt)
- Block of wood (to prevent blade rotation)
- Torque wrench (optional but recommended)
- Work gloves (blades are sharp even when dull)
- Wire brush (to clean spindle)
- Safety glasses
Step-by-Step Replacement
Step 1: Disconnect Spark Plug
Pull the spark plug wire and secure it away from the plug. This prevents accidental starting.
Step 2: Position the Mower
Push mowers: Tip onto the side with the air filter facing UP. This prevents oil from flooding the carburetor.
Riding mowers: Raise the deck to maximum height or use a lift. Never work under an unsupported deck.
[NEED REAL IMAGE: Proper mower tipping position]
Step 3: Block the Blade
Wedge a block of wood between the blade and deck. This stops the blade from spinning while you loosen the bolt.
Step 4: Remove the Blade Bolt
Turn the bolt counterclockwise. Most mowers use standard (right-hand) threads.
Stuck bolt tips:
- Use penetrating oil and wait 10 minutes
- Use a breaker bar for more leverage
- Impact wrench works great if you have one
Step 5: Remove the Blade
Note which way the blade is installed. The stamped side (usually labeled “this side up” or has a wing) faces the deck.
Step 6: Clean the Spindle
Use a wire brush to remove grass buildup and rust from the spindle and mounting surface.
Step 7: Install New Blade
- Position blade with stamped side up
- Thread bolt by hand to avoid cross-threading
- Tighten to spec (usually 35-50 ft-lbs)
- Or tighten firmly with a wrench
Step 8: Remove Block and Reconnect
Take out the wood block. Reconnect the spark plug wire. Lower the mower.
Part Numbers by Brand
Toro Blades
| Model | Blade Part | Size |
|---|---|---|
| Recycler 22 | 59534P | 22” |
| Recycler 22 SmartStow | 131-4547-03 | 22” |
| Super Recycler | 108-3762-03 | 21” |
| TimeMaster | 110-6568 | 30” |
| Personal Pace | 108-9764-03 | 22” |
Honda Blades
| Model | Blade Part | Size |
|---|---|---|
| HRX217 | 72531-VL0-B00 | 21” |
| HRR216 | 72531-VG3-000 | 21” |
| HRN216 | 72531-VL0-B00 | 21” |
| GCV160/190 engines | 72511-VH7-000 | 21” |
Craftsman/MTD Blades
| Model | Blade Part | Size |
|---|---|---|
| M110/M140 | 942-04244 | 21” |
| M220/M230 | 942-04308 | 21” |
| T110 Rider | 942-04308A | 42” set |
| T210 Rider | 942-04312 | 42” set |
Troy-Bilt Blades
| Model | Blade Part | Size |
|---|---|---|
| TB110/TB130 | 942-04244 | 21” |
| TB200/TB230 | 942-04308 | 21” |
| Pony 42 | 942-04308A | 42” set |
| Bronco | 942-04308A | 42” set |
John Deere Blades
| Model | Blade Part | Size |
|---|---|---|
| S100 Series | GX22151 | 42” |
| S240 | GY20850 | 48” |
| E100 Series | GX22151 | 42” |
| X350 | M154158 | 48” |
Husqvarna Blades
| Model | Blade Part | Size |
|---|---|---|
| YTH18542 | 532138971 | 42” |
| YTH24V48 | 539113312 | 48” |
| LC121P | 580244001 | 21” |
| Automower | 577513801 | Robot blades |
Ryobi Blades
| Model | Blade Part | Size |
|---|---|---|
| RY40108 | 613223 | 20” |
| 40V 20” | AC04142 | 20” |
| 40V 21” | AC04154 | 21” |
| RM480E Rider | AC04168 | 38” set |
[NEED REAL IMAGE: Various brand blade part number labels]
Sharpening vs Replacing
When to Sharpen
- Blade is dull but not damaged
- No bends or major nicks
- Blade still has good thickness
- You have time and tools
How to Sharpen
- Remove blade completely
- Clamp in vise
- Use file or bench grinder
- Follow original angle (about 30 degrees)
- Remove equal material from both ends
- Check balance before reinstalling
Balance check: Hang blade on a nail through center hole. Both sides should stay level. If one side drops, remove more material from that side.
When to Replace
- Bent blade (never try to straighten)
- Deep gouges or missing chunks
- Blade too thin (worn)
- Cracks visible
- Won’t hold edge after sharpening
Cost Comparison
- Sharpening service: $8-15
- DIY sharpening: Free (plus time)
- New blade: $15-40
For most homeowners, replacing blades yearly is simpler than maintaining a sharpening routine.
Riding Mower Blades
Riding mowers have 2-3 blades that work together. A few extra considerations:
Multi-Blade Timing
Blades must be timed (positioned) correctly so they don’t hit each other.
Timing procedure:
- Mark blade positions before removal
- Install blades at same positions
- Some decks have timing marks
Blade Engagement Issues
If blades won’t engage after replacement:
- Check belt routing
- Verify blade bolt torque
- Inspect PTO clutch
- Check safety switches
Spindle Inspection
While the blade is off, check the spindle for:
- Wobble (bad bearings)
- Rust or corrosion
- Damaged mounting threads
Replace spindles showing significant wear.
[NEED REAL IMAGE: Riding mower deck with multiple blades]
Aftermarket Blades
Aftermarket blades cost less than OEM. Quality varies.
Recommended aftermarket brands:
- Oregon - Reliable quality
- Rotary - Good value
- MaxPower - Budget option
- Arnold - Widely available
What to watch for:
- Verify exact measurements match OEM
- Check hole pattern and size
- Inspect for manufacturing defects
- May need light balancing
Safety Tips
- Always disconnect spark plug before working under the deck
- Wear gloves - even dull blades can cut
- Use correct bolt torque - loose blades are dangerous
- Check for damage after hitting objects
- Never run damaged blades - they can break and cause injury
Related Guides
- Sharpen Lawn Mower Blade
- Toro Recycler Repair Guide
- Honda HRX217 Repair Guide
- John Deere S100 Problems
- Lawn Mower Maintenance
Summary
Blade replacement is one of the easiest and most impactful maintenance tasks. Sharp blades cut cleaner, use less fuel and keep your lawn healthier. Replace yearly for best results or sharpen 2-3 times per season if you prefer. Either way, don’t let dull blades ruin your lawn’s appearance.