Quick Answer: How to Wind Trimmer Line
To wind trimmer line, measure the correct length for your spool (typically 20–30 feet), thread it through the center hole in the direction marked by arrows on the spool, and wind it tightly in even layers. Secure each end in the retaining slots, then reassemble the trimmer head and feed the line through the exit eyelets. The exact process varies depending on whether you have a bump-feed, automatic, or fixed-spool design.
Understanding Your Trimmer Spool Type
Before you begin winding, identify which spool mechanism your trimmer uses. The three main designs require different winding techniques and have distinct performance characteristics.
Bump-Feed Spools
Bump-feed spools are the most common design on cordless and electric string trimmers. You manually wind the line onto the spool and manually feed out more line by tapping the trimmer head on the ground. This design is straightforward to reload and doesn’t require automatic mechanisms to fail.
Automatic and Semi-Automatic Spools
Automatic spools use centrifugal force or spring mechanisms to feed line as it wears. You still load line onto the spool, but the feeder system handles line extension during use. Semi-automatic spools combine manual tapping with some automatic feed. These require careful line length measurement—too much or too little affects feeding reliability.
Fixed-Spool Designs
Some higher-end trimmers use fixed spools where line is pre-wound at the factory or loaded into a cartridge. The winding process differs significantly, and many users replace the entire cartridge rather than rewinding.
Single-Line vs. Dual-Line Configurations
Single-line trimmers use one continuous string and are lighter and quieter. Dual-line trimmers use two strings for wider cutting paths and more power but require winding two separate line sections on the same spool. Most consumer trimmers are dual-line.
What You Need Before Winding
Gather these items before starting:
- Trimmer line in the correct diameter for your model (typically .065 to .105 inches)
- Your trimmer’s owner manual for model-specific line length and diameter
- A soft cloth or small brush to clean the spool head
- Needle-nose pliers (optional, for manipulating line in tight slots)
- A measuring tape if you’re cutting line from a bulk spool
- A flat work surface with good lighting
Do not substitute line diameter or length—using the wrong size affects cutting performance, increases breakage, and can damage the spool mechanism.
How to Measure and Prepare Your Trimmer Line
Finding the Correct Line Diameter
Trimmer line diameter is measured in thousands of an inch. Common sizes are:
- .065″ (thin, for light grass and small trimmers)
- .080″ (medium, for most residential cordless trimmers)
- .095–.105″ (thick, for gas trimmers and dense weeds)
Check your owner’s manual or the trimmer head housing—most have the diameter printed on a label. Using line that’s too thin breaks easily; line that’s too thick strains the motor and spool mechanism.
Calculating Line Length
Most residential bump-feed spools hold 20–30 feet of line total (10–15 feet per side for dual-line designs). High-capacity spools may hold 40+ feet. Your manual specifies the exact length. If you don’t have it, measure the spool diameter and multiply by 3.14 to estimate circumference, then multiply by the number of wraps your spool accommodates—usually 8–12 wraps for standard spools.
Cutting and Preparing Line
If buying bulk trimmer line, use sharp scissors or a utility knife to cut straight, clean edges. Ragged cuts jam in the spool slots. For dual-line trimmers, cut two equal lengths. Let the line sit at room temperature for a few hours before winding—cold line is stiff and difficult to work with.
Step-by-Step Winding Process for Bump-Feed Spools
Step 1: Remove the Trimmer Head
Most trimmers have a release button or tab on the head housing. Press or pull it and twist the head counterclockwise (or follow your manual’s direction) to remove it from the drive shaft. Clean any grass or debris from the head and shaft with a dry cloth.
Step 2: Locate the Spool and Anchor Points
Remove the spool from the housing by twisting it counterclockwise or pressing a release tab. Inspect the spool for two anchor points—usually small slots or notches near the center hole where line ends secure. These are critical: line that slips from these slots will unspool during use.
Step 3: Insert Line Into the Center Hole
Look for directional arrows printed on the spool face or inside the housing. Thread one end of your line (for single-line trimmers) or both ends (for dual-line trimmers) through the center hole, following the arrow direction. The direction matters because it aligns the winding with the spool’s internal structure.
Step 4: Secure the Starting End
Push one line end into the first anchor slot until it seats firmly. For dual-line spools, you’ll have two separate starting points. The line should not move when you gently tug it. If it slips, reposition it deeper into the slot.
Step 5: Wind the Line Tightly and Evenly
Hold the spool level in one hand. With your other hand, guide the line as you rotate the spool in the winding direction (usually counterclockwise when viewed from above, but check your arrows). Wind slowly and deliberately, keeping tension on the line with your guiding hand. Each wrap should sit snug against the previous wrap without overlapping or crossing. Overlapping causes jams; gaps cause uneven feeding.
Wind all but the final 2–3 inches of line. For dual-line spools, wind the first side completely, then start winding the second line from the opposite anchor point in the same rotational direction.
Step 6: Secure the Ending Length
Leave 2–3 inches of line uncoiled. Insert this end into the retaining slot (usually a notch or hook near the outer edge of the spool, positioned to hold line under light tension). Push firmly until the line seats and cannot slip out. Test by gently tugging—it should hold without releasing.
Step 7: Check Your Work
Inspect the wound spool: all wraps should be parallel and evenly spaced, with no overlaps or loose sections. The spool should feel balanced when rotated. If you notice uneven winding or loose spots, unwind and rewind that section.
Winding for Automatic and Fixed-Spool Designs
Automatic Spool Winding
Automatic spools follow the same winding process as bump-feed spools but with stricter line length requirements. Measure precisely to the manual’s specification—too much line causes jams in the feeding mechanism; too little leaves you unable to tap-feed extensions. After winding, ensure the retaining slots hold line firmly; any slack allows premature auto-feed engagement.
Fixed-Spool and Cartridge Systems
Some trimmers use cartridges that clip into the head or fixed spools that don’t unwind. For these, check if your model allows rewinding or if replacement is required. Many manufacturers design these for factory service only. If rewinding is permitted, follow the same directional and tensioning principles, but work slowly—these spools often have tighter tolerances.
Reassembling the Trimmer Head
Reinstall the Spool
Guide the wound spool back into the trimmer head housing, aligning any mounting tabs or notches. Rotate it clockwise (or per your manual) until it seats fully and clicks into place. The spool should not wobble or shift.
Feed Line Through Exit Eyelets
Most trimmer heads have small holes (eyelets) on opposite sides where line exits during use. Pull the two free line ends (or the single end on single-line models) through these eyelets until they extend evenly on both sides. The line should move freely through the eyelets without binding.
Reattach the Cover Ring and Housing
Replace any gaskets or spacers in their original positions. Install the cover ring or cap by aligning it with the housing and twisting or snapping it clockwise until tight. Do not over-tighten—stop when you feel firm resistance.
Trim Line to Correct Length
Once reassembled, trim each line end to the cutting length specified in your manual—typically 3–6 inches extending past the trimmer head eyelets. Use sharp scissors for clean cuts. Ragged edges catch on eyelets and fray during use.
Reinstall the Head on the Trimmer
Align the trimmer head with the drive shaft and twist clockwise (or per manual) until it seats and locks in place. Ensure the release button or tab is fully engaged. The head should not rotate or come loose when gently twisted by hand.
Common Mistakes to Avoid
Winding in the Wrong Direction
If you wind against the arrow direction, the spool mechanism disengages and line either won’t feed or unwinds during use. Always check arrows before starting. If unsure, wind slowly and test on a small section first.
Incorrect Line Length
Too much line overloads the spool, causes jams, and strains the motor. Too little means you can’t tap-feed enough line or the auto-feeder engages prematurely. Use your manual’s exact specification.
Loose or Uneven Winding
Line that crosses itself or has gaps causes jams and poor feeding. Take time to wind slowly, keeping even tension and ensuring each wrap sits flush against the previous one.
Line Slipping From Anchor Slots
If line pulls free from the retaining slots, it unspools mid-use and fouls the trimmer head. Push line ends firmly into slots and test by tugging hard before reassembling.
Forgetting to Clean the Spool Head
Grass buildup around the spool housing prevents proper seating. Always clean before rewinding.
Troubleshooting After Installation
Line Won’t Feed or Keeps Breaking
Check that the spool is wound tightly with no gaps—loose sections cause feed jams. Verify line diameter matches your manual. If line breaks frequently, it may be old or brittle; replace it with fresh line. Also ensure the exit eyelets are clean and not damaged.
Trimmer Vibrates or Sounds Unusual
Unbalanced winding or unevenly distributed line causes vibration. Rewind, keeping tension even and wraps parallel. If the head wobbles when rotated by hand, reinstall it—it may not be fully seated.
Line Extends Too Quickly or Won’t Extend
For automatic spools, check that line length matches specs—too much or too little disrupts the feeder. For bump-feed, ensure the spool rotates freely when you tap it; a stuck spool indicates wound line is too tight or the spool is misaligned.
One Line Extends Faster Than the Other
On dual-line spools, uneven winding on each side causes differential feed. Rewind the slower side, matching the tension and wrap count of the faster side.
Frequently Asked Questions
How often should I rewind my trimmer line?
Rewind when you run out of line or when the remaining line becomes too short to cut effectively (usually 1–3 inches). For frequent users, this may be every 2–4 weeks during mowing season. Store unused line in a cool, dry place—sunlight and heat degrade the material.
Can I use any trimmer line diameter on my trimmer?
No. Using the wrong diameter affects cutting performance and can damage the spool or motor. Always use the diameter specified in your manual. If you can’t find your manual, check the trimmer head housing for a label, or contact the manufacturer with your model number.
What’s the difference between bump-feed and automatic feed?
Bump-feed requires you to tap the trimmer head on the ground to release more line—it gives you control but requires action during use. Automatic feed uses centrifugal force or springs to extend line as it wears, requiring no user action. Automatic spools often cost more but save time during longer trimming sessions.
Why does my trimmer line keep breaking?
Common causes include: using line that’s too thin for your trimmer, winding it too loosely so it frays, or using old line that’s become brittle. Also check that exit eyelets aren’t cracked or rough—damaged eyelets cut line as it feeds. Replace eyelets if necessary, or have a repair shop handle it.
Can I mix line diameters or use aftermarket line?
Stick to the diameter and line type (round nylon is standard) specified in your manual. Aftermarket line is generally compatible if it matches diameter and material, but cheap line often breaks faster. Buy from reputable brands and test on a small section before loading a full spool.
