The basic steps to load new string

Replacing the string on a weed eater is a straightforward task that takes about five to ten minutes once you know the motion. Most weed eaters use one of two designs: a fixed spool that you wind by hand, or an automatic or semi-automatic head that advances string as you tap it on the ground. The process differs slightly between them, but both start the same way: stop the engine, let it cool, and remove the spool or head from the trimmer shaft.

The string itself comes in spools at any hardware store or garden center, usually labeled by diameter—.065 inch and .080 inch are the most common sizes. Check your trimmer's manual or the existing spool to find the right thickness, because using the wrong size can jam the head or break the string constantly. Buy a spool that matches what came out.

Key Takeaways

  • Stop the engine, let it cool, and remove the spool or head from the trimmer shaft before touching the string.
  • Check your trimmer's manual or the old spool to find the correct string diameter—usually .065 or .080 inch—because the wrong size will jam or break.
  • On a manual spool, wind the string tightly in the direction marked on the spool, leaving 4 to 6 inches free on each side for the cutting head.
  • On an automatic or semi-automatic head, insert the string into the slot, wind it around the spool, and thread the ends through the eyelets before reassembling.
  • After reassembly, test the string by running the trimmer briefly at low speed before using it at full power.

How to wind string on a manual spool

A manual spool is the simpler design. Once you remove it from the trimmer, look for an arrow or the words "wind this direction" molded into the plastic. This matters—winding backward will tangle the string and jam the head. Cut a length of string about 15 to 20 feet long from your new spool.

Insert one end of the string into the small notch or hook at the edge of the spool—this holds it in place while you wind. Then turn the spool in the direction the arrow points, keeping tension on the string with your other hand so it winds tightly and evenly. Wind until you have about 4 to 6 inches of string left free. Repeat with the second string chamber on the other side of the spool if your trimmer has two.

Once both sides are wound, thread each free end through the eyelets (the small holes) on the trimmer head. These eyelets guide the string out to the cutting edge. Reassemble the spool onto the trimmer shaft, making sure it clicks or locks into place, then pull gently on each string end to make sure it feeds smoothly.

How to load string on an automatic or semi-automatic head

Automatic and semi-automatic heads work differently because they advance the string for you as you use the trimmer. Instead of winding by hand, you insert the string into a slot on the spool, wind it around the spool a few times, and then thread the ends through the eyelets. The exact steps vary by brand, so check your manual, but the general motion is the same.

Cut a length of string about 15 to 20 feet long. Find the slot or opening on the spool where the string enters—it is usually marked with an arrow or labeled "insert here." Push one end of the string into that slot and hold it in place. Wind the string around the spool two or three times in the direction the arrow indicates, keeping it tight and flat so it does not overlap itself. After winding, thread both free ends through the eyelets on the trimmer head.

Reassemble the head onto the trimmer shaft and make sure it locks. On a semi-automatic head, you may need to press a button or tab to release the next length of string—check your manual for this step. On a fully automatic head, the string advances on its own as you trim, so you do not need to do anything after reassembly.

Checking the string length and tension

Before you use the trimmer at full power, run it briefly at low speed to make sure the string feeds smoothly and does not jam. If the string does not come out of the eyelets or feels stuck, stop when ready and check that you wound it in the correct direction and that nothing is blocking the slot.

The string should be taut but not so tight that it strains the head. If it feels loose or droops, the string may not cut efficiently and will wear out faster. On a manual spool, you can adjust tension by rewinding slightly tighter. On an automatic head, tension is usually set by the design, so if it feels wrong, the spool may not be seated correctly on the shaft.

When to call a professional

If the trimmer head is cracked, the eyelets are broken, or the shaft is bent, replacing the string will not fix the problem. These parts need to be replaced by a repair shop or the manufacturer. Similarly, if the string jams repeatedly even after you have reloaded it correctly, the head may be damaged inside and need professional service.

If you are unsure which string size your trimmer uses or cannot find the manual, take a photo of the trimmer head and the old spool to a hardware store or garden center—staff there can usually match it for you in a few minutes.

Frequently Asked Questions

Can I use a different string diameter than what came on the trimmer?

No. Using a thicker or thinner string than the trimmer is designed for will either jam the head or break constantly. The diameter is stamped on the old spool or listed in your manual. Stick to that size.

How often do I need to replace the string?

It depends on how often you trim and what you are cutting. Light residential use might mean replacing it once or twice a season. Heavy use or hitting rocks and hard objects will wear it out faster. You will know it is time when the string becomes noticeably shorter or frayed.

What if the string keeps breaking right after I load it?

Check that you wound it in the correct direction—the arrow on the spool matters. Also make sure the eyelets are not cracked or sharp, because a rough edge will cut the string. If both are fine, the string diameter may be wrong for your trimmer.

Do I need to empty the old string before loading new string?

Yes. Remove all the old string from the spool before winding new string. Leftover pieces can jam the head or prevent the new string from feeding smoothly. On an automatic head, make sure the spool is completely empty.

Can I use string from any brand, or does it have to match my trimmer brand?

Any brand works as long as the diameter matches. String is string—the brand does not matter. Buy whatever is available at your local hardware store in the correct size.