String Trimmer Head Types Overview
| Head Type | How Line Feeds | Best For |
|---|---|---|
| Bump-feed | Tap head on ground to advance line | General residential use — most common |
| Fixed-line (pre-cut) | Insert pre-cut segments through head holes | Low maintenance; heavy brush cutting |
| Auto-feed (auto-cut) | Motor-speed centrifugal system advances line automatically | Convenient; no tapping required |
| Rapid reload / easy load | Line threads through holes, no spooling | Quick line changes in the field |
What You’ll Need
| Item | Notes |
|---|---|
| Replacement trimmer head | Compatible with your trimmer brand and shaft size |
| Flat-bladed screwdriver or punch pin | For pressing the shaft lock button |
| Adjustable wrench or pliers | For loosening the head bolt |
| Work gloves | Protect hands during head removal |
Safety Precautions
- Disconnect all power before starting: Remove battery, unplug cord, or disconnect spark plug wire. The head must not be able to spin while your hands are near it.
- Note the thread direction before removing: Some trimmer heads use reverse (left-hand) threads — they tighten counterclockwise and loosen clockwise. Turning the wrong way can damage the shaft threads.
- Keep fingers away from the gear case opening: A trimmer shaft can spin unexpectedly if power is not fully disconnected.
How to Remove the Old Trimmer Head
Method 1 — Shaft Lock (Most Common)
Most modern trimmers have a shaft lock button on the gearhead near the head. Press and hold this button to lock the shaft, then turn the head to unscrew it. For standard (right-hand) threads: turn the head counterclockwise (from looking down at the bottom of the head) to remove. For reverse-thread heads: turn clockwise.
If you’re unsure of the thread direction, check your trimmer manual. Oregon, Stihl, Husqvarna, Ryobi, and DeWalt models vary — confirm before applying force.
Method 2 — Pin or Hole Lock
Some models have a hole through the gear head housing. Insert a punch pin, screwdriver, or the pin that came with your trimmer (often stored in the head itself) through this hole to lock the shaft, then unscrew the head.
Method 3 — Wooden Block
If no lock is present, hold the head steady with a piece of wood (never bare hands) pressed against the blade guard on the inside, then use a wrench on the head’s center bolt to unscrew. This works for models where the head screws onto the shaft with a flat bolt head in the center (rather than threading the entire head body).
How to Install the New Trimmer Head
Step 1 — Verify Compatibility
Trimmer heads must match your trimmer’s shaft type (straight vs. curved), thread direction, and adapter size. Many aftermarket heads (like Oregon, Arnold, and Husqvarna Pro) come with multiple adapter inserts to fit different shaft sizes. Match the adapter insert to the diameter and thread type of your trimmer shaft — the adapters are usually marked.
Step 2 — Thread the New Head On
Hand-thread the new head onto the shaft in the correct direction. For standard right-hand threads: clockwise to tighten. For reverse-thread: counterclockwise to tighten. Use the shaft lock to secure the shaft, then snug the head firmly with your hand or wrench — don’t over-tighten, but make sure it won’t vibrate loose during use.
Step 3 — Load Line (Bump-Feed Heads)
Open the head (most have a twist-lock cap) and spool the correct diameter line. Most residential bump-feed heads take 0.080″–0.095″ round line. Wind the line in the direction indicated by the arrow inside the head housing — always follow the arrow, as winding backwards causes tangling. Leave about 6 inches of line protruding through each eyelet. See our line loading guide for the full process.
Step 4 — Test Before Full Use
Reconnect power and run the trimmer briefly (away from any surfaces) at medium throttle to verify the head spins true, feeds line correctly on the first bump, and doesn’t vibrate unusually. A head that vibrates may not be threaded fully or may have an incompatible adapter seated incorrectly.
When to Replace vs. Repair a Trimmer Head
| Issue | Replace or Repair? |
|---|---|
| Cracked head housing | Replace — cracked housing causes line to jam and can fail at speed |
| Bump button broken or worn | Often repairable — replacement bump buttons are $3–$8 separately |
| Line won’t feed through eyelets | First try cleaning — if eyelet is worn oval-shaped, replace head |
| Head threads damaged | Replace head AND inspect shaft threads before installing new head |
| Wanting to upgrade to fixed-line head | Replace — fixed-line heads eliminate reloading hassle |
If your line keeps failing to feed rather than the head itself being damaged, see our string trimmer line feed troubleshooting guide.
Pro Tips
- Consider upgrading to a fixed-line head: Fixed-line heads (like the Oregon 24-895 or Husqvarna T35) use pre-cut line segments pushed through holes — no spooling, no tapping, instant line changes. They’re slightly more expensive to run (more line consumed per change) but far more convenient for infrequent trimmers.
- Keep the adapter inserts from universal heads: Universal aftermarket heads come with 3–5 adapters. Keep the extras in a small bag in your trimmer storage — you may need them if you ever upgrade to a different trimmer model with the same head.
- Check head torque after the first use: New heads can vibrate slightly loose on the first use. After the initial 10-minute run, verify the head is still fully tight.
Frequently Asked Questions
Are string trimmer heads universal?
No — they’re not fully universal, but many aftermarket heads (Oregon, Arnold, Husqvarna Pro) come with adapter kits that fit most major brands. You must match the shaft thread direction and size. Check the adapter kit’s compatibility chart before purchasing. For brand-specific models (Stihl, some Milwaukee), OEM replacement heads are more reliable.
How do I know what direction my trimmer head threads?
Check your trimmer’s manual — it specifies the thread direction (right or left-hand). As a general rule: Stihl trimmers use left-hand (reverse) threads. Husqvarna, Ryobi, DeWalt, and most other brands use right-hand (standard) threads. A small arrow on the head or shaft adapter often indicates tighten direction.
How much does a replacement trimmer head cost?
OEM replacement heads: $10–$30 for most residential brands. Universal aftermarket heads with adapters: $8–$25. Premium fixed-line heads (Oregon 24-895, etc.): $15–$35. The head type upgrade from bump-feed to fixed-line often costs less than $20 and can significantly improve your trimming experience.
Can I replace a bump-feed head with a blade attachment?
Only if your trimmer is specifically rated for blade attachments — check the manual. Many residential trimmers are NOT rated for blade use (grass blades, brush blades, etc.) due to the engine and gearhead specifications. Using an unsupported blade attachment on a light-duty trimmer is a safety hazard.
My new head vibrates during use — what’s wrong?
Vibration usually indicates the head isn’t fully threaded/tightened, or the wrong adapter is seated in the head. Remove, check that the adapter matches your shaft size exactly, and re-install hand-tight then an additional 1/4 turn. If vibration continues, verify the head is compatible with your specific trimmer model.
Conclusion
String trimmer head replacement is one of the most accessible trimmer repairs — 10–15 minutes, basic tools, and a $10–$35 part. Verify thread direction before removal, choose a compatible replacement head or adapter kit, and consider upgrading to a fixed-line head if you frequently struggle with bump-feed reloading. Install correctly, test briefly before full use, and your trimmer is back to full cutting performance.
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