Keeping your mower blades sharp and in good condition will help you achieve a nice clean cut for a great-looking lawn. When your blades become damaged or extremely worn you may end up with an uneven cut. Dull blades can even cause your lawn to turn brown a day or two after you cut your lawn.
Read on and I’ll share everything you need to know about your John Deere mower blades including replacing, sharpening, and balancing your blades.
I also provide information on items that can damage your blade and what you should be looking for when checking your blade’s condition.
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Follow all safety instructions provided in your equipment operator’s manual prior to diagnosing, repairing, or operating.Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
How Often Should You Change Your John Deere Mower Blades?
Your John Deere mower blades should be replaced with a new set of blades each year. I find it best to replace blades during your annual John Deere maintenance. That way it’s easy to keep track of how old your blades are.
It’s a good idea to keep the set of mower blades you remove. If the blades are in good condition, sharpen them and set them aside. Having a backup set of blades is handy. You never know when you might accidentally bend or damage a blade.
How Often Should You Sharpen Your John Deere Mower Blades?
Sharpen your John Deere lawn mower blades after approximately 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 John Deere Mower Blades Need to be Sharpened?
New John Deere mower blades do not need to be sharpened. They have been sharpened during the manufacturing process and coated with 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 mower.
Inspect Your John Deere Mower Blades for Damage
It is possible for your John Deere mower blades to become very worn or damaged from normal use. Check the condition of your mower blades regularly. Sharpen or replace them when they begin to appear dull, worn, or damaged.
Here are the conditions to look for when inspecting your John Deere blades:
Wearing on the John Deere Blade Sail
Check the blade sail. This is the high part of the mower blade that creates air movement under your deck when the blades rotate. The dirt that gets sucked into the deck causes the sail to wear and thin out.
It’s time to replace your blades when you notice the sail appears thinner than the center of the mower blade.
Chips & Dings in the John Deere Blade Edge
You can try to avoid hitting objects in the yard with your mower, but it is bound to happen. You may hit a stone or other small object that can chip your mower blade. Small chips in the blade should be able to be smoothed out by sharpening the blade.
When you find a large gouge in your blade edge, it is time to replace it. Large chunks missing from your mower blade will not only affect your cut quality, but it can also cause your blades to become unbalanced causing additional damage to your John Deere.
John Deere Blade is Bent
When you impact a hard object, you can tweak or bend your mower blade. You must replace a bent John Deere blade if it is slightly or significantly bent to maintain a good cut and avoid causing additional damage.
Never attempt to straighten a mower blade. Doing so will compromise the blade by weakening the metal. You don’t want a weakened blade spinning under your mower deck at high speeds.
There is a chance the weakened metal can break off and fly out of your mower putting people and objects at increased risk of injury or damage.
There are a couple of ways to check for a bent mower blade. Follow one of these steps:
- Check for a bent John Deere blade by removing it 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 John Deere blade while installed on the deck
You can also check for a bend in your blade while it is installed on your John Deere. To do this, park your mower 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 a 1/8” difference, you need to remove and replace your lawn mower blade with a new blade.
If you do find a bent blade, you should check your John Deere’s spindle housing for damage. When an object is hit hard, you can bend a spindle or bearing.
John Deere 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 John Deere at high speeds.
Items that Can Damage Your John Deere Mower Blade
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 mower blade:
- Sticks, Rocks and Toys
Items left in your yard like sticks, stones, and even toys can damage your John Deere blade. The mower 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 mower when your blades become unbalanced or you have spindle damage. - Sand & Debris
Sand and debris wear out mower blades prematurely. A lawn that is thinly covered in the 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 conditions.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 & Change Your John Deere Mower Blades
Here are the steps to remove your John Deere Blades:
Gather tools to remove blades
- Ratchet
- Block of Wood
- Work Gloves
- Safety Glasses
- Torque Wrench
- Cordless Impact Gun (Optional)
Prepare John Deere for Blade Removal
Always take safety precautions when working with your sharp lawn mower 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 mower on a flat surface. Engage the parking brake. Use blocks of wood or wheel chocks to prevent your mower 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 John Deere Mower Blades
Use a block of wood to lodge between your blade and the mower deck edge to keep your mower blade from moving while removing the blade. Loosen the hardware securing the blade using a socket and ratchet. Remove your hardware and blade.
Reinstall John Deere Mower 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 John Deere’s recommendation which can be found in your owner’s manual.
Note: When reusing the blades you have sharpened, make sure they are balanced before installing. Instructions for balancing your John Deere blades can be found below.
How to Safely Sharpen John Deere Lawn Mower Blades DIY
You can save some time and money by sharpening your own John Deere 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
- Rags
- Wire Brush
- Safety glasses
- Work gloves
Put on Safety Glasses and Gloves
Clean Your John Deere 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 John Deere Blade
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 it 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 it in the vice, and sharpen using the same procedure.
Sharpen with an angle grinder or bench grinder
- Hold the 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 it in the vice, and sharpen using the same procedure.
Balance Your John Deere Mower Blades
It is necessary to make sure your John Deere mower 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 You Should Seek a Professional Sharpening Service for Your John Deere
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 of 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 sharpen 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
- The blade is properly balanced. This will reduce vibration and damage to your mower deck.