Rewinding grass trimmer line requires removing the spool, anchoring the new line, winding it tightly in the direction shown by the arrow, then reassembling and threading through the eyelets — the exact steps vary by trimmer model.
A jammed or poorly wound trimmer head costs you time on every lawn. The rewind process itself is straightforward, but getting the direction, tension, and length wrong guarantees tangles or a head that won’t feed. Here’s the sequence that works across most consumer trimmers — with the one detail per model you absolutely cannot skip.
Before You Start: Safety and Prep
Turn the trimmer off completely. For cordless models, remove the battery. For gas models, shut the engine off and let it cool — a hot muffler against your hand is a fast way to end the job. Clear the work area of debris, and have the correct replacement line ready: the exact diameter your model accepts is stamped on the head or listed in the manual, and using a thicker line can burn out the motor or snap on contact.
Removing the Old Line and Spool
Press the side tabs or unscrew the cap on the trimmer head, depending on your model. Lift the spool out and pull off any old line and debris inside the head. If the head uses a bump-feed mechanism, watch for a spring and spindle — keep them in the order you found them. Misplacing that spring is the single most common reassembly mistake.
Winding the New Line: The Right Direction and Tension
Cut one length of line per the manual’s recommended total (commonly 10–25 ft across single and dual spools, but check your model’s spec). Insert one end into the anchor hole or slot on the spool. Wind neatly and tightly in the direction of the arrow printed on the spool — if no arrow is marked, wind clockwise by default. Keep the wraps even and non-overlapping; crossed layers cause binding and “exploding” unwinds during use. Leave about 6 inches unwound on single-line spools, then secure the tail in the notch if the spool has one. For dual-line spools, repeat the same process on the second channel with a second equal length.
If your trimmer uses a fixed-line head (no spool), you skip this entirely: replace pre-cut line pieces through the eyelets or slots instead.
Reassembly and Threading: The Step That Gets Skipped
Place the wound spool back into the head, ensuring the spring and spindle are in their original order. Thread each line end through its matching eyelet on the head — this is the step most people forget, and closing the cap without threading means you start over. Snap or screw the cap back on until it seats firmly. Gently pull the line ends to test feed; if they resist, something is binding. A brief test run on low throttle will finish feeding the line to cutting length.
If you’re shopping for a new cordless trimmer that makes this process easier, our picks for the best cordless electric grass trimmers cover models with tool-free spool replacement and bump-feed heads that save frustration.
Common Rewind Mistakes That Waste Your Time
- Winding the wrong direction. The spool arrow is not optional — winding opposite to it prevents the line from feeding at all.
- Overfilling the spool. Too much line creates tangles and jams. Stick to the manual’s capacity even if you think more line means longer runtime.
- Loose or overlapping wraps. Even tension prevents the line from binding inside the head during centrifugal feed.
- Skipping the eyelet thread. Closing the cap with the lines still inside the head guarantees a complete teardown.
- Losing the spring or spindle. On bump-feed heads, the spring returns the spool after each advance; without it, the mechanism fails.
| Spool Type | How It Winds | Key Reassembly Detail |
|---|---|---|
| Single-line spool | One length wound into one channel | Leave ~6″ tail, secure in notch if present |
| Dual-line spool | Two equal lengths, one per side | Route each end through its own eyelet |
| Fixed-line head | No spool — pre-cut pieces through slots | Ensure equal length on both sides |
| Bump-feed head | Standard spool plus spring/spindle | Reinstall spring and spindle in original order |
FAQs
How do I know which line diameter my trimmer uses?
The correct diameter is printed on the trimmer head or listed in your model’s owner manual. Using a thicker line than specified can overload the motor and cause permanent damage; thinner line will snap too quickly to be useful.
Can I rewind a trimmer spool without the manual?
Yes, if the spool has a directional arrow and the head uses standard eyelets. Look for the arrow before winding, and don’t overfill. For exact line length and diameter, you’ll need the manual or a quick check on the manufacturer’s support site.
Why does my trimmer line keep jamming after I rewound it?
The most common causes are winding opposite the arrow, overlapping wraps, or overfilling the spool. Take the head apart, confirm the direction, and rewind with even tension at the correct length. Also verify the cap’s eyelets are clear of debris.
References & Sources
- wikiHow. “How to Change the String on a Lawn Trimmer.” Covers the general rewind and reassembly process for consumer trimmers.