Taking care of your mower blades and regularly replacing or sharpening them is required to continue to give you a nice cut. There are signs your mower blades need some attention. These signs include the tips of your grass blades turning brown a few days after mowing and strips of grass left behind from worn blades.
The tips of the grass turn brown when the blades are worn. Instead of a giving your lawn a nice precise cut, a dull blade will beat up and tear the grass. This causes the ends to turn brown from bruising. Strips of grass can be left behind when blade tips are extremely worn.
When working on your mower deck, you need to take safety precautions to prevent your lawn tractor from turning on and moving. Refer to your owner’s manual for all safety precautions including removing your ignition key, disconnecting the spark plugs and setting your parking brake.
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How Often Should You Change Your Lawn Tractor Blades?
Lawn tractor blades should be changed once a year. Install a new set of lawn tractor blades annually while servicing your tractor.
If the blades you are removing at the end of the mowing season are still in good condition, sharpen them. Keep them on hand in case you damage a mower blade during the season and can no longer use it.
Use the old set of blades when you find your current blades are damaged and you don’t have a new set on hand. By doing this, you can finish up mowing your lawn and don’t have to wait for a new set of blades.
How Often Should You Sharpen Your Lawn Tractor Blades?
Sharpen your lawn tractor blades after every 25 hours of use. For the average homeowner, this amounts to about twice a year. You may need to sharpen them more often if you mow more than the average homeowner or if you mow in dry and dusty conditions.
Do New Lawn Tractor Blades Need to be Sharpened?
Lawn tractor blades purchased as new do not need to be sharpened prior to installing them. They have been sharpened during the manufacturing process and coated with a paint. There is no need to remove the paint along the edge of the blade. The new blade is ready to install and use on your lawn tractor.
Check Your Lawn Tractor Blades for Damage
It is possible for your lawn tractor blades to become very worn or damaged from normal wear and tear. Check the condition of your lawn tractor blades regularly. Sharpen or replace them when they begin to appear dull, worn or damaged.
Here are the conditions to look for when checking your blades for wear and damage:
Wearing on the Lawn Tractor Blade Sail
The blade sail is the high side of the blade that is used to create air movement under the deck as it rotates. The sail can wear from sand sucked into the deck. It’s time to replace the lawn tractor blade when the sail appears thinner than the center of the blade.
Chips & Dings in the Lawn Tractor Blade Edge
Walking your lawn before your mow to remove objects that your lawn tractor may hit is recommended to reduce damage to the tractor. Even though you take every precaution to avoid hitting an object, it can still happen.
Stones and small objects can create chips in the blade edge. Small chips in the blade can usually be smoothed out by sharpening the blade edge. Larger chips and gouges require your blade be replaced to continue to receive a good cut from the blade.
Lawn Tractor Blade is Bent
Hitting a solid stationary object can cause impact to the blade and bend it. You must replace a bent lawn tractor blade with a new blade. Never attempt to straighten the blade as you will weaken the metal. This weakened area is more prone to crack. A cracked blade spinning at very high speeds can cause serious injury or damage.
Here are a couple ways to check for a bent lawn tractor mower blade:
- Check for a bent lawn tractor blade by removing from the deck
Remove your blade from your mower deck and place it on top of a new blade to check for a bend in the blade. When the used blade doesn’t lay flat against the new blade and you notice a bend, you must replace the blade.
- Check for a bent lawn tractor blade while installed on the deck
You can also check for a bend in your blade while it is installed on your lawn tractor. To do this, park your lawn tractor on a hard level surface. Take a measurement from the ground to the blade tip and then rotate your blade 180 degrees and take another measurement from the ground to the blade tip.
If the measurement is greater than 1/8” difference, you need to remove and replace your lawn tractor blade with a new blade.
If you do find a bent blade, you should check the spindle housing for damage. When the blade impact is significant, you may have damage to the bearing or spindle.
Lawn Tractor Blade is Cracked
A blade that has a crack in it must be replaced right away. You risk metal breaking off and flying out of your lawn tractor at high speeds.
Items that Can Damage Your Lawn Tractor Blades
You can prevent some damage to your blades by removing items from your yard, but you can’t prevent all damage. Here are a few items that can damage a lawn tractor mower blade:
- Sticks, Rocks and Toys
Items left in your yard like sticks, stones and even toys can damage your lawn tractor blade. The blades spin fast. The speed of the blade and impact with a solid item can cause your blade to become chipped or bent. Significant impact can send vibrations through your lawn tractor when your blades become unbalance or you have spindle damage.
- Sand & Debris
Sand and debris wear out lawn tractor blades prematurely. A lawn that is thinly covered in grass will suck more dirt into the mower deck than a lawn that is covered with a thick blanket of grass. Blades wear faster in dirty dusty condition.
There really isn’t much you can do to combat the sandy conditions besides waiting for your grass to grow in and become a thick covering on your yard. Just make sure you are regularly sharpening your blades and replacing them when they become extremely worn.
- Lawn Chemicals
Some chemicals used on lawns to assist with the health and growth of the grass can cause corrosion of the blade and mower deck. This corrosion can cause your blades to fuse to the deck. Remove your blades periodically to ensure they don’t bond to the deck so you are no longer able to remove them.
How to Remove & Install Your Lawn Tractor Blades
Here are the steps to remove your lawn tractor blades:
Gather tools to remove blades
- Block of Wood
- Work Gloves
- Safety Glasses
- Torque Wrench
- Cordless Impact Gun (Optional)
Prepare Your Lawn Tractor for Blade Removal
Always take safety precautions when working with your sharp lawn tractor blades. Working under your deck can be dangerous. Follow these safety precautions before proceeding:
- Wear heavy duty work gloves when working with sharp blades
- Park your lawn tractor on a flat surface. Engage the parking brake. Use blocks of wood or wheel chocks to prevent your tractor from rolling.
- Remove your ignition key
- Disconnect your spark plug wires
- Raise your mower deck safely or remove your mower deck if necessary to gain access to the underside of your mower deck.
Remove Your Lawn Tractor Blades
Use a block of wood to lodge between your blade and the mower deck edge to keep your blade from moving while removing the blade. Loosen the hardware securing the blade using a socket and ratchet. Remove your hardware and blade.
Reinstall Your Lawn Tractor Blades
Install a new or sharpened set of blades. Install each blade using a block of wood to prevent the blade from spinning as you install and tighten the hardware. The sails, or high sides of the blades, must face upward when placing the center of the blade over the spindle shaft.
When using cupped washers, make sure the cupped side is installed toward the mower blade. Install your hardware and torque to your manufacturer’s specification which can be found in your owner’s manual.
Note: When reusing the blades you sharpened, make sure they are balanced before installing. Instructions for balancing your lawn tractor blades can be found below.
How to Sharpen Your Lawn Tractor Mower Blades DIY
You can save some time and money by sharpening your own lawn tractor mower blades. There are several different tools that can be used to sharpen your blades including a metal file, drill powered blade sharpener or a disc grinder. Follow these steps to sharpen your blades:
Gather the tools you will need
- 10″ flat metal file, drill powered blade sharpener, or disc grinder
- A vice to hold the blade in place
- Blade balancer or nail on the wall
- Wire Brush
- Safety glasses
- Work gloves
Put on Safety Glasses and Gloves
Clean Your Lawn Tractor Blades
Use a rag to clean the dirt off your mower blades. A wire brush can be used for stubborn areas of buildup.
Secure Your Lawn Tractor Blades
Securely place your blade in a vice to keep it from shifting during sharpening. After sharpening one side, you will flip the blade and secure in the vice while you sharpen the other side.
File or Grind Blade to Sharpen Edge
Sharpen with a metal file
- Using a file, push the file at an angle in one direction along the blade.
- Do not use a sawing motion when filing.
- Once all the rough spots and uneven edges are removed, flip the blade over, secure in the vice, and sharpen the other side.
Sharpen with a drill powered blade sharpener.
- Power the drill with the blade sharpener attached.
- Place the flat guide of the sharpener along the flat portion of the blade with the cutting edge slot into the bevel.
- Move the sharpener up and down the length of the blade edge.
- Once one side is sharpened without any rough spots or nicks, flip the blade over, secure in the vice, and sharpen using the same procedure.
- Hold angle grinder perpendicular to the edge of the blade. Run the grinder along the length of the blade to level out any rough spots or nicks. Keep the grinder moving so it removes a little metal at a time and produces an even result.
- Once one side is sharpened without any rough spots or nicks, flop the blade over, secure in the vice, and sharpen using the same procedure.
Balance Your Lawn Tractor Blades
It is necessary to make sure your lawn tractor blades are balanced after sharpening them. Unbalanced blades can cause excessive vibration, spindle damage and potential engine damage.
A balanced blade is a blade with equal weight on each side of the mower blade. To properly check a blade to make sure it is equally weighted, use a blade balancer. This inexpensive item can save you from a large repair expense due to not having your blades properly balanced. To balance your blades, shave metal off the heavy side of the blade until the weight of the blade is equal on both sides.
If you don’t have a blade balancer on hand, use a nail on the wall. Set the nail head about an inch away from the wall and place the blade’s center hole on the nail. Shave metal off the side that hangs lower until the blade sits level.
When to Seek a Professional Sharpening Service for Your Lawn Tractor Blades
I can sharpen my mower blades myself and I even have the tools to do so, but I still choose to have my local lawn mower dealership sharpen my blades. The dealer does a much better job than I do and it’s convenient. I drop them off at the dealership and pick them up a couple days later.
The timeline works for me because I always have a second set of sharpened blades on hand so the wait doesn’t bother me. You may choose to have a professional sharpen your blades because:
- It is a safer option to sharpening the blade yourself
- Sharpening a blade is often less expensive than purchasing a blade
- A professional can grind down mower blades to get rid of large nicks and gouges in the steel
- Blade is properly balanced. This will reduce vibration and damage to your mower deck.
Annual Service is Required to Keep Your Lawn Tractor in Good Condition
You can minimize the problems you encounter with your lawn tractor by completing a full service before the mowing season. Read my article on servicing your lawn tractor where I address these items:
- Change engine oil and filter
- Replace spark plugs
- Remove debris from cooling fan & engine
- Remove debris from hydro fans and transmission
- Clean battery terminals and check the battery
- Replace the air filter
- Replace the fuel filter
- Check your fuel system
- Check tire pressures
- Check mower deck pulleys and belt
- Scrape the mower deck
- Replace or sharpen mower blades
- Grease the tractor
- Check the safety system
- Wash the tractor