1. Worn or Damaged Blades:
- Over time, mower blades can become dull, chipped, or bent. This can cause them to lose their balance and vibrate, leading to contact.
- If the blades are worn or damaged, they need to be sharpened or replaced.
2. Improper Blade Installation:
- The blades must be installed correctly, with the correct bolt torque and facing the right direction.
- If they are installed incorrectly, they can collide.
3. Incorrect Blade Height:
- If the blades are set too low, they can hit the deck or the ground.
- Adjust the blade height according to the manufacturer's recommendations.
4. Bent Deck:
- If the mower deck is bent, it can cause the blades to hit the deck.
- Inspect the deck for any signs of damage and have it repaired if necessary.
5. Loose Components:
- Any loose bolts, nuts, or other components on the mower deck can cause the blades to vibrate and hit each other.
- Tighten all loose components.
6. Improper Spindle Bearings:
- Worn or damaged spindle bearings can cause the blades to wobble and hit each other.
- Replace any worn or damaged bearings.
7. Worn or Damaged Deck Drive Belt:
- If the deck drive belt is worn or damaged, it can cause the blades to run at different speeds.
- This can lead to the blades hitting each other.
To diagnose the issue further, you can:
- Visually inspect the blades: Check for any signs of damage or wear.
- Check the blade height: Make sure it's set according to the manufacturer's recommendations.
- Inspect the deck: Look for any signs of damage or wear.
- Check all bolts and nuts: Make sure they are tight.
- Listen for any unusual noises: This can help identify the problem.
If you are unable to identify the cause of the problem, it's best to consult a qualified John Deere mechanic.