Threading a weed eater usually means replacing the cutting line so the trimmer can feed and cut again. On a typical bump-feed head, disconnect power, open the cap, wind or insert the correct line, feed the ends through the eyelets, and reassemble. Head design, wind direction, and line size vary by model, so follow the markings on the head and the owner’s manual.
What Threading a Weed Eater Means
A weed eater, also called a string trimmer, cuts grass and light weeds with a spinning length of nylon or similar polymer line. That cutting line is stored in a trimmer head at the end of the shaft. One or more eyelets let short working ends stick out so they can whip through vegetation.
When people ask how to thread a weed eater, they almost always mean how to restring it: load new line, clear a jam, or install a fresh spool so the tool feeds again. You may also hear reload, restring, or replace the spool. The job is about the cutting head, not the engine, motor, or drive shaft.
You typically need to thread the head when the line snaps off inside the eyelets, welds itself into a fused lump, jams so it will not advance, or simply runs out. A trimmer that still starts but no longer cuts, or that only cuts on one side of a dual-line head, is often a line problem rather than a power problem.
Not every machine stores a long coil on a removable spool. Some accept short pre-cut pieces. Some load a single length through the eyelets and wind from the outside. The goal is the same: seat the correct diameter line so the feed mechanism can release it without tangling.
Safety Steps Before You Open the Head
Treat the head as if the trimmer could start until you have isolated power. A spinning head, a spring-loaded cap, and leftover heat from a gas muffler are the main hazards.
For a battery model, stop the motor and remove the battery pack. For a corded electric trimmer, unplug it at the tool or the outlet so it cannot be bumped back on. For a gas model, switch the engine off and wait until moving parts stop. If the owner’s manual tells you to disconnect the spark-plug boot before service, do that and keep the boot away from the plug until you are finished. Let a hot engine and muffler cool before you kneel next to the head.
Wear eye protection. Gloves help when you handle sharp line ends, grit, and a cover that may still be under spring tension. Work on a stable surface with the trimmer supported so the head cannot roll or drop.
A compressed spring under the bump knob or spool can launch the cover or the spring itself when the last tab releases. Keep your face out of line with the cover and ease it off rather than prying hard. Do not start the trimmer, squeeze the trigger, or reinstall a battery while the head is open or the spool is in your hand. Follow the model manual for fuel, battery, and spark-plug handling rather than improvising a lockout method.
Identify Your Head Type Before You Start
Generic winding steps only help if they match the head you actually have. Look at the bottom and sides of the trimmer head before you force anything apart. The later bump-feed sequence is common, but it is not universal.
Bump-feed heads
Most consumer weed eaters use a bump-feed head. A button or knob on the bottom is meant to be tapped on the ground while the head is spinning so more line can release. Inside you will usually find a spool, a spring or washer stack, and a cover held by threads or side clips.
Auto-feed heads
Some heads advance line automatically as the remaining ends wear down. The outer look can resemble a bump-feed head, but the inner mechanism and the way line must be wound are often more particular. If there is no bump button, or the manual describes automatic feed, do not assume a standard rewind will work.
Fixed-line heads
A fixed-line head does not store a long coil. It holds short factory-cut or user-cut pieces in molded slots or clamps. There is nothing to wind. You remove worn pieces and lock new ones in place.
Easy-load or through-the-eyelet heads
Some newer consumer heads let you push one length of line straight through both eyelets, then wind with a knob or by rotating part of the head. You may not need to remove the spool at all. If you see a winding knob and a through-hole path, look for that procedure on the head or in the parts diagram before you pry the housing open.
Single-line versus dual-line
A single-line head has one exit eyelet. A dual-line head has two, usually opposite each other, and the spool is often divided into two channels or uses a center notch so two working ends pay out together. Dual-line designs need both ends routed correctly or the head will cut on one side only and feel out of balance.
Also decide whether you are winding bulk line by hand or installing a pre-wound spool made for that head. A matching pre-wound spool skips the winding step but still has to drop in the right orientation with the ends through the eyelets. Look for arrows, the word wind, a line-size stamp, and any exploded diagram in the owner’s manual. Those markings override generic advice.
What You Need
You do not need a large toolkit. Gather the owner’s manual or parts diagram, replacement trimmer line that matches the diameter marked on the head, spool, or manual, scissors or line cutters, and eye protection and gloves. A pre-wound spool sold for that specific head design is optional if you want to skip hand winding.
If the cover uses stubborn clips, a flat tool may help you release a tab without gouging plastic, but forcing a stuck housing often breaks the clips that hold it together. Clean the head first so you can see the release points.
Line diameter matters more than brand marketing. The eyelets, spool channels, and feed mechanism are built for a limited size range. Line that is too thick can jam, refuse to feed, or strain the head. Line that is too thin can slip, break at the eyelet, or melt together from heat and friction. If a package lists several diameters, treat those as options to confirm against your head, not as a universal fit.
Line also comes in different shapes, such as round, twisted, or serrated profiles. Shape can change how the line cuts and how it wears, but no shape replaces a correct diameter or a correct wind. Bulk line is enough if you are willing to cut and wind it. A pre-wound spool is worthwhile when you can match the part to the head. An ill-fitting aftermarket spool can sit too high, miss the eyelets, or leave the cover unable to latch.
How to Open a Typical Bump-Feed Head
Start by brushing grass, mud, and wrapped line off the head so tabs and threads are visible. Caked debris is a common reason a cover feels stuck shut.
On many heads you press two side tabs and lift the outer cap. On others you hold the housing and unscrew the bump knob or the cover. Some covers unscrew counterclockwise; others use a different thread or a clip-and-twist motion. There is no single direction that applies to every brand, so look for arrows or try gentle pressure before you apply force.
Lift the cover straight off. Under it you should see the spool and, on a large share of bump-feed designs, a spring. There may also be a washer or retainer. Note which way the spring sits and which face of the spool was up. A quick photo or a parts layout on a towel keeps the order obvious.
Slide the spool out and pull any leftover line from the eyelets. If old line is fused to the spool, cut it free rather than tearing plastic posts. Inspect the spool, eyelets, and bump button for cracks, flattened tabs, or deep grooves. Those defects will still be there after you rewind.
Do not yank a stuck cover. Bent or broken tabs are a frequent reason a freshly loaded head will not stay together. If the spring pops out, find it before you continue. A missing or upside-down spring is a classic no-feed problem later.
Cut, Split, and Prepare the Line
How much line you cut depends on the spool, not on a single length that works for every weed eater. The useful amount is whatever fills the spool in even layers without standing above the rim or crowding the cover. If the head, spool, or manual prints a length, use that. If it does not, wind as you go and stop before the coil overflows.
For a dual-line or split-spool head you usually need either two equal pieces or one longer piece folded at a center notch or slot. The fold or the two inner ends anchor the line so both sides pay out together. A single-line spool typically takes one piece hooked into a single anchor hole or slot.
Cut the ends cleanly. A square, unfrayed tip is easier to push through an eyelet than a mashed end. If the line has been coiled tightly in storage, let a working length relax so it does not spring off the spool as you wind.
If you bought a matching pre-wound spool, skip the cutting and winding steps. Confirm it is the same style as the one you removed, including the number of line ends and the location of the anchor features. Avoid overfilling. Extra line stuffed past the spool flanges will rub the housing, bind when you close the cover, and often refuse to feed.
Wind or Insert the Line
This is the step that decides whether the head will feed. Most spools have arrows or a this-way mark. Wind in that direction. Winding against the marks is one of the most common reasons a bump-feed or auto-feed head will not release line. There is no universal clockwise or counterclockwise rule that covers every brand.
Hook the inner end or the folded midpoint into the spool’s anchor slot or hole so it cannot slip. Then wind under light, even tension. Keep the line flat in layers instead of letting it pile in the middle or climb one flange. For a divided dual-line spool, keep each line in its own channel. If the two lines cross and stack, they can lock together when you later bump the head.
Leave enough free end on each side to reach through the matching eyelet with a little extra to hold. Some spools have temporary holding notches on the rim; use those if they are there so the coil does not unwind while you handle the spool.
If the line is wound loosely, it can expand, tangle, or slip under itself. If it is wound the wrong way, bumping the head may tighten the coil instead of paying line out, or the inner mechanism may try to retract rather than advance. Seat a pre-wound spool the same way you would a hand-wound one: correct face up, ends ready for the eyelets, and no leftover packaging left inside the head.
Feed the Line Through the Eyelets and Reassemble
Hold the wound spool above the housing and line up each free end with its eyelet. Push the tips through from the inside so they exit the metal or plastic eyelets on the outside of the head. On a dual-line head, each end should come out the eyelet that matches its side of the spool. Crossing the ends so they fight each other will make the head feed poorly and run roughly.
If you used rim holding notches, release the line from those notches as you feed the eyelets so the coil can sit naturally. Drop the spool into the housing. Refit the spring or washer exactly as you found it. The spring usually sits in the bump-button path under or over the spool, depending on the design. If it is left out, stacked wrong, or pinched beside the spool, the bump function will feel dead or the cover will not close.
Set the cover on the housing. Align any tabs, keys, or thread starts. Snap or screw it down until it is fully seated all the way around. A cover that clicks on one side only can fly off when the head spins. Pull each exposed end gently to confirm the line slides and is not pinched under the cover or between spool flanges.
Leftover line that sticks out much too far can whip, wrap the shaft, slap the debris shield, or unbalance the head. After the cover is locked, trim the ends to a workable length. Many trimmers have a cutoff blade on the debris shield, and some manuals show a starting length. Use those guides when they exist rather than guessing a single number for every machine.
Do a last visual check: tabs locked, bump button free to move if the head uses one, no line trapped under the rim, and both dual-line ends present.
Easy-Load, Auto-Feed, and Fixed-Line Differences
If your head does not match the open-and-wind sequence, stop following bump-feed steps and use the method the head was built for.
On many easy-load or through-the-eyelet heads, you align marks on the housing, push one piece of line in one eyelet and out the other until the lengths are roughly even, then turn a knob or rotate the head to wind the line inside. The spool stays in the housing. Forcing that kind of head apart can break parts you did not need to remove.
Auto-feed heads may still use a spool, but the inner cam, spring, or clutch that meters line can be intolerant of the wrong diameter and of a reverse wind. If the manual shows a specific loading path, follow that diagram. Repeating a bump-feed rewind on an auto-feed mechanism is a frequent source of it-still-will-not-feed complaints.
Fixed-line or pre-cut heads use short pieces locked into slots, holes, or clamps. Cut or buy pieces that match the head’s intended size and length as marked, insert them until they lock, and make sure each piece is seated so it cannot fly out. There is no coil and usually no bump button.
Quick-load marketing names are not standardized. Two heads that both claim fast loading can still use different alignment marks, knob directions, and line lengths. Whenever you see a winding knob, no removable spool, or molded slots instead of a bump button, go to the model diagram rather than improvising.
Why Line Diameter and Wind Direction Matter
The trimmer head is a small mechanical dispenser. Eyelets, spool posts, and the bump or auto-feed works are sized for a narrow band of line.
Oversized line binds in the eyelets, stacks too thick on the spool, and can keep the cover from sitting flat. Undersized line can slip the feed mechanism, chatter in the eyelets, break as soon as it hits a fence or dry stalk, or weld into a solid ring when friction heats the coil. Heat-welded line is a common surprise after a long session on abrasive ground: the outer wraps look fine until you open the head and find a fused doughnut that will not pay out.
Wind direction is not cosmetic. The bump button and many auto-feed systems rely on the coil relaxing or rotating in a predicted way. Wind the wrong way and a bump can tighten the spool, retract the ends, or lock the line against a post. That is why the arrows on the spool matter more than a memory of how the last brand was wound.
Wrong line will not always destroy a trimmer, but it can crack a cheap spool, groove eyelets faster, and leave you repeatedly stopping to reopen the head. Manufacturer size ranges belong on the stamp on the head or in the manual. Confirm those markings instead of assuming a diameter that worked on a different machine will work on this one.
Check Your Work Before You Cut
Reinstall the debris shield or guard if you removed it. A missing guard is not a shortcut; it is a reason to stop. Confirm the head is fully assembled and that no tools or spare coils are still on the shaft.
Reconnect power only when you are ready to test: battery in, cord plugged in, or spark-plug boot back on according to the manual. Start the trimmer in a clear area away from people, pets, windows, and loose gravel. Let the head come up to speed and listen for a cover that is not seated or a spool that is rattling.
If you have a bump-feed head, tap it on bare soil or a paved surface only in the way the manual describes. You are checking that line can advance, not trying to empty the spool. If nothing comes out after a reasonable attempt, stop the machine, isolate power again, and reopen the head. Repeatedly slamming a head that is wound backward or overfilled will not fix the winding; it can break the bump button or the cover tabs.
Watch the first few seconds of cutting. Line that immediately disappears, smokes, or welds, or a head that walks hard to one side, means you should shut down and inspect rather than keep going. A cracked head is a stop-work condition, not something to tape over.
Common Problems After Threading
If the line will not come out when you bump the head, the usual causes are a coil wound the wrong way, a spool that is overfilled, ends that never made it through the eyelets, a missing or inverted spring, a cover that is not fully latched, or debris packed around the bump button. Open the head and look before you assume the trimmer itself has failed.
If line keeps breaking at the eyelet, the eyelet may be grooved or sharp, the line may be too thin or old and brittle, or you may be trimming against chain-link, concrete, or wire. Replace a badly worn eyelet or spool if those parts are serviceable, and keep the spinning line off hard edges when you can.
If the cover will not stay on, tabs may be cracked, the spool may be too full, or a spring may be sitting beside the spool instead of in its pocket. Do not tape a cover on and run it.
Fused line from heat, leftover string wrapped under the spool, and a cracked spool hub can all mimic a feed failure. Cleaning the housing and starting the rewind over is often faster than guessing. Line problems do not, by themselves, diagnose a bad engine, clutch, or motor. If the head is correctly loaded and still will not spin, that is a different repair.
When to Use the Manual or Replace the Head
Generic restringing steps stop being enough as soon as the head in your hand disagrees with them. The owner’s manual, the line-size stamp, and the arrows on the spool take priority. That is also where you will find the official winding diagram, the intended line diameter range, and any easy-load alignment marks.
Replace the head, or the worn service parts inside it, when retaining tabs are broken, the bump button is stuck or missing, eyelets are sharply grooved, the housing is cracked, or the cover will not stay assembled even with a correctly filled spool. Rewinding will not restore plastic that has already failed.
There is no single replacement interval that applies to every weed eater. Use, impact with hidden objects, and heat all change how long a head lasts. When you shop for a replacement, match the mounting and the head style to the model rather than assuming any aftermarket head will thread onto the shaft and feed the same way.
If the task involves a damaged shaft, a leaking gas tank, damaged wiring, or a head that will not come off with the method in the manual, stop and use a qualified repair shop. Restringing is a line job. It is not a reason to defeat guards or work on a live fuel or electrical system.
Frequently Asked Questions
Is threading the same as restringing or replacing trimmer line?
Yes. Threading, restringing, reloading, and replacing the spool are everyday names for getting new cutting line into the trimmer head so it can feed through the eyelets.
Do gas, electric, and battery weed eaters thread differently?
The line job is usually similar because it lives in the head. What changes first is how you make the tool safe: remove the battery, unplug the cord, or shut down a gas engine and follow the manual for the spark-plug lead. Head type matters more than whether the trimmer is gas, electric, or battery powered.
Which way should I wind the line?
Follow the arrows or wind markings on the spool or housing. Do not rely on a single clockwise or counterclockwise rule for every brand. Wrong-direction winding is a common reason a bump-feed head will not release line.
How much line should stick out after assembly?
Enough to cut, but not so much that it wraps the shaft or hits the shield in a wide, uncontrolled arc. After the cover is locked, trim to a workable length using the cutoff blade on the guard or the length shown in the manual when one is given.
Can I use any diameter of trimmer line?
No. Use the diameter range marked on the head, spool, or manual. Oversized line jams. Undersized line breaks, slips, or can weld together from heat.
What if my head has no removable spool?
You may have an easy-load, through-the-eyelet, or fixed-line design. Load through the eyelets and wind with the knob, or lock in short pre-cut pieces, as the head and manual show. Do not force the housing apart unless the diagram calls for it.
