Sharp items will become dull with extended use. This is true of Kubota lawn mower blades. Sharp blades are an important element to getting a nice cut from your mower. When your blades are dull, they will beat up your grass and not give it a precise cut.
A good indication your Kubota mower blades are dull is when the tips of your grass turn brown a day or two after mowing. When this happens, grab a handful of grass and look at the blade tips.
They will be brown and have little tears in them when dull blades have been used to cut the grass. The blades are tearing the grass instead of cutting it.
You purchased a Kubota zero-turn because of its strong brand and cut quality. Don’t let dull mower blades impact that quality. Before working with your Kubota mower deck, take safety precautions to protect yourself from injury.
This includes preventing your mower from starting, protecting your hands and eyes, and ensuring your mower does not move. Refer to your owner’s manual for all safety procedures.
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Follow all safety instructions provided in your equipment operator’s manual before 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 Kubota Lawn Mower Blades?
The mower blades on your Kubota lawn mower should be changed once a year. Blades that wear quickly because they are exposed to excessive dirt, rocks, and gravel will need to be replaced more frequently.
I like to start each year out with a new set of blades. I install them while completing the annual service on my mower.
If the blades I’m replacing are not too worn, I sharpen them and keep them on hand in case a set is damaged. This way I can get my mowing done while I wait to get a new set of blades.
How Often Should You Sharpen Your Mower Blades?
Sharpen your Kubota mower blades after every 25 hours of use. For the average homeowner, this amounts to twice a year. When operating your mower in sandy conditions, you will need to check your mower blades and sharpen them more frequently.
Do New Kubota Mower Blades Need to Be Sharpened?
A new Kubota mower blade does not need to be sharpened before it is installed on your mower. The blade is sharpened during the manufacturing process and coated with paint. This paint will wear off the edge of your blade while mowing.
Check Your Mower Blade for Excessive Wearing and Damage
A bad mower blade can affect your cut quality. There are several items you need to watch out for when inspecting your mower blades for wearing and damage.
If you are experiencing a bad or uneven cut with your Kubota, check out my article on items that can cause your Kubota to give you an uneven cut.
Wearing the Blade Sail
The sail of the blade is the high side of the blade. The sail creates air movement to form a suction under the deck. When the sail becomes worn, the blade must be replaced. A worn sail is one where the sail is not as thick as the center of the blade.
Chips & Gouges in the Edge
Operating your Kubota lawn mower in areas with rocks and other solid objects can cause chips and gouges in the edge of your mower blade.
If the chips are small, you can usually fix them by sharpening your blade edge. When they are larger gouges, and cannot be repaired by sharpening, you must replace your mower blade.
Bent Mower Blade
A bent blade can happen when you hit a solid object like a tree root or rock. A bend can compromise your Kubota’s cut.
Sometimes the bend of the blade is so significant you can visually confirm it is bent. Other times, it may be slightly bent and you have a harder time identifying a bend by just looking at it.
There is a couple of ways you can check for a bent blade with and without the blade installed on your Kubota mower.
Check for a Bent Blade While the Blade is Installed
With your lawn mower parked on a flat-level surface, measure one end of your mower blade from the ground to the blade. Record the measurement. Next, rotate the blade 180 degrees and measure the blade from the same point on the ground to the blade.
Record the measurement. If the two measurements are greater than a 1/8” difference, you must replace your mower blade.
Check for a Bent Blade with Your Blade Removed
Remove your mower blade and match it up with a new mower blade. Place the used blade on top of the new blade. If you find any bends and gaps between the two blades, replace your Kubota blade.
When you impact your blade enough to bend it, you could also have caused damage to the spindle and bearing in your spindle housing. A good way to check whether you have a problem that requires you to disassemble your spindle housing is to check it with your mower blade installed.
Checking for Spindle or Bearing Damage
With a heavy pair of work gloves to protect your hands, grab each end of the mower blade and rock it up and down. You will feel movement or hear a knocking when you have a problem in your spindle or housing.
If your blade isn’t securely in place and you feel movement, remove your blade and your spindle housing. Check your spindle and bearing in the housing for damage. Repair any damage found.
Never attempt to straighten a mower blade and reuse it. Straightening the blade compromises the metal. It makes the blade weak and more likely to crack and break off which can be extremely dangerous.
Cracked Mower Blade
Look for signs of cracking on your mower blade. A cracked blade must be replaced immediately. When a cracked blade spins at high speeds, a piece of the blade can break off and fly out of your mower deck. This can put people and objects in the area at increased risk of injury or damage.
Items That Can Prematurely Wear & Damage Your Kubota Mower Blade
It is good practice to walk your yard prior to mowing to remove any items that can cause damage to your mower deck and blades. There are several items that can prematurely wear or damage your Kubota blades:
Sticks, Rocks, and Toys: These items can be accidentally run over causing the blade to become bent or gouged. An impact can cause damage to your spindle bearing which will send a vibration through your mower when your deck is engaged.
Sand and Debris: There isn’t too much you can do about this besides growing a nice thick lawn. This can take years and isn’t a quick fix. Regularly check, sharpen or replace your Kubota mower blades as needed.
Lawn Chemicals: Some homeowners choose to use chemicals on their lawns to assist with the growing process and lawn health. Some of these chemicals can be corrosive to your Kubota mower.
This corrosion can cause your mower blades to fuse to the mower so they don’t come off your mower easily.
Regularly remove your blades and reinstall them to prevent them from fusing to the mower and increase the likelihood of damage when you attempt to remove them after an extended period of time.
How to Remove Your Kubota Mower Blades
- Work Gloves
- Safety Glasses
- Torque Wrench
- Block of Wood
- Cordless Impact Gun (Optional)
Take Safety Precautions
Always remove the spark plug boots and the ignition key from your Kubota lawn mower. This prevents the mower from starting with you under the mower deck.
Stay safe by following these safety tips in addition to wearing safety glasses and using work gloves to protect your hands from the sharp edges on your blades.
Remove & Install Blades
Use a block of wood to wedge between the blade and the mower deck to prevent the blade from moving. Remove the mower blade using a socket and ratchets. If it doesn’t come off easily, you may want to use a cordless impact gun.
You can also attempt to remove stubborn bolts by placing a block of wood over the head of the bolt. Hit the block with a hammer to shock and loosen the bolt so you can turn it.
Remove the bolt, blade boss, or flat washer, concave washers, and mower blades. Note: Depending on your model mower, you may not use all the hardware listed.
Confirm the hardware is in good condition. The cupped washers need to be replaced if they are worn or flattened. A flattened washer will allow the blade to slip.
Follow the instructions below to sharpen and balance your Kubota blades. Your blades must be properly balanced before installation so you don’t damage your mower.
Install your blades and hardware in the opposite order you took them off. The cupped washers need to be installed with the cupped side facing toward the mower blade.
Make sure the blades are installed with the sails (high sides of the blade) facing up and pointing toward your mower deck.
How to Sharpen Your Kubota Mower Blades DIY
You can save some time and money by sharpening your own Kubota mower blades. There are several different tools that can be used to sharpen your blades including a metal file, a 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
Clean the Mower Blades
Put on your work gloves and safety glasses. Use a rag to clean the dirt off your mower blades. A wire brush can be used for stubborn areas of buildup.
Secure the Mower Blade
Securely place your Kubota 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 the Blade Edge to Sharpen
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 it 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.
How to Balance Your Mower Blades
It is essential to balance your mower blades before placing them on your Kubota mower. Failing to do so can damage your spindle bearings and cause a severe vibration.
A balanced blade is a blade that has equal weight on each side of the blade. Use a blade balancer to check for equal weight. Shave metal off the heavy side of the blade until you reach an equal weight.
Another option to use, if you don’t have a blade balancer, is a nail in the wall. Place a nail in the wall with the nail head about 3/4″ to 1″ away from the wall.
Place the center hole of the blade over the nail. Your blade is balanced when the blade is parallel to the ground. Shave the metal off the heavier end until both sides of the blade sits at the same level on the nail.
When You Should Seek a Professional Sharpening Service for Your Kubota Lawn Mower Blades
It is up to you whether or not you sharpen your blades yourself or have a professional sharpen them. I have the tools to sharpen my mower blades, but I choose not to sharpen my own blades.
My local Kubota dealership does a better job of putting a clean edge on the mower blade than I do. I drop off my mower blades and pick them up a couple of days later.
I always keep an extra set of blades on hand so I can continue mowing so the turn-around time doesn’t really affect 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.