How to Install a Blade on Your STIHL Trimmer Head

Is your STIHL trimmer ready for a new blade? Whether you’re upgrading from a line head or replacing a worn-out blade, getting your trimmer set up correctly is key to efficient and safe operation. While it might seem daunting at first, installing a blade on your STIHL trimmer head is a straightforward process that anyone can tackle with a few simple tools and a bit of patience.

In this article, we’ll walk you through the steps to safely and correctly install a blade on your STIHL trimmer head, getting you back to tackling those tough weeds and overgrown areas in no time.

You can also watch a video demonstration of the process: How to replace the string trimmer head of a STIHL weed whacker with a blade

Before You Begin: Safety First!

Before you even think about grabbing your tools, let’s talk safety. Trimmers, especially those with blades, can be dangerous if not handled properly.

• Always disconnect the spark plug wire. This is crucial! You do NOT want the engine accidentally starting while you’re working on the head.
• Wear appropriate personal protective equipment (PPE). This includes sturdy gloves to protect your hands from sharp edges, and safety glasses to shield your eyes from any debris.
• Work on a stable, flat surface. This will prevent your trimmer from tipping over while you’re working.

What You’ll Need:

• Your STIHL trimmer
• The new STIHL blade
• Combination wrench (often comes with your STIHL trimmer) or a socket wrench set
• Blade mounting kit (if converting from a line head – this typically includes a rider plate, thrust washer, and collar nut)
• Locking pin (usually provided with your trimmer or blade kit)

Step-by-Step Blade Installation:

The exact components and order might vary slightly depending on your specific STIHL model and whether you’re converting from a line head or just replacing a blade. However, the general principles remain the same.

If You’re Converting from a Line Head:

If your trimmer currently uses a line head and you’re switching to a blade, you’ll need to install the blade mounting kit components first.

1. Remove the existing line head: This usually involves unscrewing it counter-clockwise.
2. Install the thrust washer: This is a flat, round washer that sits directly on the gearhead shaft.
3. Place the rider plate: This goes on top of the thrust washer. It has a raised center that helps secure the blade.
4. Position the blade: Align the center hole of the blade with the raised center of the rider plate. Ensure the cutting edge of the blade is facing the correct direction (refer to your blade’s instructions if unsure, but typically the arrows or markings indicate the cutting direction).
5. Install the collar nut: This nut secures the blade and the other components. It’s usually a left-hand thread, meaning you tighten it by turning it counter-clockwise.

If You’re Just Replacing an Existing Blade:

1. Locate the locking pin hole: On the gearhead of your trimmer, you’ll find a small hole.
2. Insert the locking pin: Rotate the blade or rider plate until the holes in both the gearhead and the blade/rider plate align. Insert the locking pin into this hole to lock the shaft and prevent it from rotating. This is crucial for loosening and tightening the nut.
3. Remove the collar nut: Using your combination wrench or socket wrench, turn the collar nut clockwise to loosen it (remember, it’s usually a left-hand thread, so “righty-tighty” for normal nuts is “lefty-loosey” for this one).
4. Remove the old blade, rider plate, and thrust washer: Keep track of the order of these components.
5. Clean the shaft: While the components are off, it’s a good idea to clean any debris from the shaft and surrounding area.
6. Reassemble with the new blade:
   • Place the thrust washer back onto the gearhead shaft.
   • Position the rider plate on top of the thrust washer.
   • Place the new blade onto the rider plate, ensuring the cutting direction is correct.
   • Thread on the collar nut.
7. Tighten the collar nut: With the locking pin still in place, use your wrench to tighten the collar nut by turning it counter-clockwise until it’s snug. Don’t overtighten, but make sure it’s secure.
8. Remove the locking pin: Don’t forget this!

Final Checks:

• Spin the blade by hand: Does it spin freely without any wobble?
• Double-check all connections: Ensure everything is tight and properly seated.
• Reconnect the spark plug wire: You’re almost ready!

You’re Ready to Trim!

Now that your new blade is securely installed, you can confidently get back to maintaining your property. Remember to always operate your STIHL trimmer according to the manufacturer’s instructions and wear appropriate safety gear.

If you encounter any difficulties or are unsure about any step, don’t hesitate to consult your STIHL owner’s manual or visit your local STIHL dealer for assistance. Happy trimming!

Disclaimer: This article provides general guidance. Always refer to your specific STIHL trimmer’s owner’s manual for detailed instructions and safety precautions. Small engine repair can be dangerous if not performed correctly. If you are uncomfortable with any of these steps, please consult a qualified technician.