How to Change a Dewalt Weed Eater String? Easy Replacement Guide

Introduction

If you’ve ever struggled to edge your lawn or clear weeds because your Dewalt weed eater string is frayed, broken, or dull, you know how frustrating it can be to put off a simple repair. Many homeowners assume replacing the string requires a trip to a repair shop or a costly new trimmer head, but the truth is, How to Change a Dewalt Weed Eater String? is a straightforward 10-minute DIY task that saves you $20 to $30 per replacement plus service fees. This guide covers every Dewalt model, from 20V MAX residential trimmers to 40V XR commercial-grade units, with step-by-step instructions, troubleshooting tips, and best practices to keep your tool running at peak performance for years. Whether you’re a first-time DIYer or an experienced yard tool user, you’ll have your weed eater back in action faster than you can order a replacement part online.

Table of Contents

• Understanding Your Dewalt Weed Eater String System
• What Tools and Supplies You’ll Need
• Safety Precautions Before You Start
• Step 1: Power Off and Disconnect the Weed Eater
• Step 2: Remove the Spool Housing or Trimmer Head
• Step 3: Extract the Old, Worn-Out String
• Step 4: Prepare the New Replacement String
• Step 5: Wind the New String Correctly
• Step 6: Reassemble the Trimmer Head
• Step 7: Test the New String for Proper Function
• Common Troubleshooting Tips for Dewalt Weed Eater Strings
• How to Choose the Right Replacement String for Your Dewalt Model
• Best Practices to Extend Your Weed Eater String’s Lifespan
• Frequently Asked Questions
• Conclusion

Understanding Your Dewalt Weed Eater String System

Before you start the replacement process, it helps to understand how your Dewalt weed eater’s string system works, as design varies slightly across models. Most modern Dewalt trimmers use a bump-feed or automatic feed spool system, where the string is wound around a removable plastic spool inside the trimmer head. When you bump the head lightly on the ground (for bump-feed models) or as the automatic system detects wear, a small length of string is released to replace the portion worn down from cutting grass, weeds, and light brush.

Older Dewalt commercial models may use a fixed-line head, where the string is permanently attached to the head and cannot be rewound – these require a full trimmer head replacement when the string wears out. Most residential and newer commercial Dewalt models, however, use interchangeable quick-load spools that let you either wind new string yourself or pop in a pre-wound replacement spool in seconds. Knowing which system your model uses will help you follow the correct steps for your specific tool.

What Tools and Supplies You’ll Need

Gathering all your supplies before you start will make the process faster and avoid mid-project trips to the hardware store. You’ll need the following items:

• Replacement Dewalt-compatible trimmer string (correct diameter for your model, see section 12 for guidance)
• Screwdriver set (Phillips head and/or Torx, depending on your model’s spool screw)
• Flathead screwdriver (for prying off clip-on spool covers)
• Work gloves (to protect your hands from sharp string edges)
• Safety glasses (to protect your eyes from flying debris)
• Rag or paper towels (for cleaning grass and debris from the trimmer head)
• Pliers (optional, for pulling out tangled old string)
• String winder tool or drill with socket bit (optional, for faster, more even winding)
• Pre-wound replacement spool (optional, for quick no-wind installation)

Safety Precautions Before You Start

Even though Dewalt weed eaters are electric or battery-powered and don’t have the same risks as gas-powered models, taking a few basic safety steps will prevent injury and damage to your tool.

Wear Protective Gear

Always put on safety glasses before handling the trimmer head, as loose string ends can snap and fly into your eyes. Work gloves will protect your hands from cuts from sharp string edges, and closed-toe shoes will guard your feet if you drop the trimmer head accidentally.

Disconnect All Power Sources

Never attempt to replace the string while the weed eater is plugged in or the battery is attached. Even a light bump of the trigger can cause the trimmer head to spin unexpectedly, leading to serious cuts. For cordless models, remove the battery pack by pressing the release latch and pulling it straight out of the base. For corded models, unplug the power cord from the wall outlet and wrap it loosely to avoid tripping hazards.

Work on a Stable Surface

Lay the weed eater on a flat, clean workbench or table to avoid losing small screws, clips, or spool parts. If you’re working outdoors, place a clean tarp down to catch debris and small parts that might fall into the grass.

Step 1: Power Off and Disconnect the Weed Eater

This is the most critical step to avoid accidental startup. First, if you’re using a cordless model, press the battery release latch (located on the bottom of the weed eater’s motor housing) and pull the battery pack straight out until it detaches fully. For corded models, unplug the power cord from the wall outlet, and if possible, tape the plug to the ground to avoid it getting pulled loose during the repair.

Once power is fully disconnected, lay the weed eater on a flat surface with the trimmer head facing up. Inspect the trigger to make sure it’s not stuck in the on position, and give it a few test presses to confirm it’s fully disengaged before moving on.

Step 2: Remove the Spool Housing or Trimmer Head

Most Dewalt trimmers have a spool cover that protects the internal spool from grass and debris. To access the spool, you’ll first need to remove this cover:

1. Locate the spool retention screw or knob on the bottom or side of the trimmer head. For most models, this is a small Phillips or Torx screw; check your model’s manual if you’re unsure of the screw type.
2. If your model uses a screw, loosen it by turning it counterclockwise with the appropriate screwdriver. Do not remove it fully unless the spool cover is loose, as some screws hold the entire trimmer head to the shaft.
3. If your model uses a clip-on spool cover, insert a flathead screwdriver into the gap between the cover and the trimmer head housing, and gently pry the clips loose. Start at one corner and work your way around the cover to avoid breaking the plastic clips.
4. For Dewalt quick-load models, the entire spool assembly twists off counterclockwise – no need to remove a separate cover. Just grip the spool and twist it left until it detaches from the housing.

Set the spool cover, screw, or spool assembly aside in a safe spot so you don’t lose small parts.

Step 3: Extract the Old, Worn-Out String

Before removing the old spool, take note of how the string is wound: which direction it’s wrapped around the spool, and how much length is sticking out of the trimmer head slots. This will make winding the new string much easier later.

Pull the old string ends out of the slots on the trimmer head, then lift the spool out of the housing. If any leftover string is stuck in the spool’s center hole or slots, use pliers or a small flathead screwdriver to gently pry it out. Dispose of the old string properly, as loose string can be a hazard to pets, wildlife, and small children if left in your yard.

While the spool is removed, wipe the inside of the trimmer head housing with a rag to remove any built-up grass, mud, or tangled string debris. A clean housing will ensure the new string feeds smoothly and doesn’t jam.

Step 4: Prepare the New Replacement String

Using the correct string for your Dewalt model is essential for optimal performance and to avoid damaging your tool. Most residential 20V MAX Dewalt weed eaters use 0.080-inch (2.0mm) diameter round string, while heavier-duty 40V MAX and commercial models use 0.095-inch (2.4mm) or 0.105-inch (2.6mm) string. Using a string that’s too thick can overload the motor, while a string that’s too thin will break easily and not cut effectively.

Cut a length of string that is twice the length of the old string plus an extra 12 inches (30cm) to account for winding and trimming excess. For most Dewalt models, this equals 10 to 12 feet (3 to 3.5m) of total string. If you purchased a pre-wound replacement spool, skip this step and confirm the spool is labeled as compatible with your specific Dewalt model before installing it.

Step 5: Wind the New String Correctly

Winding the string in the wrong direction or overlapping it is the most common cause of feeding jams and premature breakage, so follow these steps carefully:

1. Check the spool for a printed arrow indicating the correct winding direction (clockwise or counterclockwise). If there is no arrow, refer to your model’s manual or match the winding direction of the old string you removed earlier.
2. Insert one end of the string into the small center hole of the spool, and pull it through about 2 inches (5cm) to create a secure anchor point.
3. Hold the spool in one hand and the anchored string end in the other, then wind the string tightly and evenly around the spool, following the marked direction. Avoid overlapping the string, as this creates weak spots and jams. If you’re using a string winder tool or drill, keep tension on the string as you wind to ensure it’s tight and even.
4. For dual-line cutting models (most Dewalt trimmers), leave 6 to 8 inches (15 to 20cm) of string sticking out of each of the two slots on opposite sides of the spool. For single-line models, leave only one end sticking out of the single slot.

Pro tip: If you don’t have a string winder, clamp the anchored string end to your work surface with a vice grip (pad the string with a rag to avoid damage) to keep tension while you wind.

Step 6: Reassemble the Trimmer Head

Once the new string is wound correctly, it’s time to put the trimmer head back together:

1. Place the wound spool back into the trimmer head housing, making sure the string ends are aligned with the correct slots on the head. If you’re using a quick-load spool, align the tabs on the spool with the slots in the housing, then twist it clockwise until it clicks into place.
2. If your model uses a separate spool cover, place the cover over the spool and align the clips or screw hole. For clip-on covers, press the clips firmly around the entire edge of the cover until you hear a clicking sound, confirming it’s secured. For screw-on covers, tighten the screw clockwise until snug – do not overtighten, as this can crack the plastic cover.
3. If you removed the entire trimmer head assembly from the weed eater shaft, reattach it by twisting it clockwise until it is fully seated and tight.
4. Pull both string ends firmly to confirm they are locked in the head slots, and spin the spool by hand to make sure it rotates freely without catching. If the spool doesn’t spin, you wound the string too tight or overlapped it, so you’ll need to unwind and redo the winding step.

Step 7: Test the New String for Proper Function

Before you take the weed eater out to your yard, test it to make sure the string feeds correctly and cuts effectively:

1. Reattach the battery pack or plug the weed eater back into the wall outlet. Put on your safety glasses before proceeding.
2. Hold the weed eater away from your body and any obstacles, then turn it on at low speed. Let it run for 10 to 15 seconds to check for abnormal vibration or noise.
3. For bump-feed models, bump the trimmer head lightly on a hard surface (like a sidewalk or the edge of your workbench) 2 to 3 times to see if more string releases automatically. For automatic feed models, let it run for 30 seconds to see if the system releases string as it wears down from the air.
4. If the string does not feed, turn off the weed eater and disconnect power, then check if you wound the string in the wrong direction, if the string is tangled inside the spool, or if the feed mechanism is clogged with debris. Adjust as needed.
5. Once the string feeds correctly, test it on a small patch of grass or weeds. Trim any excess string with scissors so that only 6 inches (15cm) of string extends from the trimmer head – longer string causes excessive vibration and reduces cutting efficiency.

Common Troubleshooting Tips for Dewalt Weed Eater Strings

Even if you follow the steps correctly, you may run into minor issues. Here are fixes for the most common problems:

• String won’t feed: Check that you wound the string in the correct direction, that it’s not overlapping in the spool, and that the spool is seated correctly in the housing. Clean out any grass or debris clogging the feed mechanism with a small brush.
• String breaks frequently: Confirm you’re using the correct diameter string for your model, that the string is wound tightly enough, and that you’re not hitting rocks, concrete, or thick brush with the trimmer. If the trimmer head is cracked or damaged, replace it to avoid further breakage.
• String wears out very quickly: Use high-quality Dewalt OEM or reputable third-party string instead of cheap generic options, avoid cutting wet grass or weeds (which are tougher on string), and mow before edging to reduce the amount of thick growth you have to cut.
• Trimmer vibrates excessively: For dual-line models, make sure both string ends are the same length. If one is shorter, trim it to match the other. If vibration persists, check if the spool is warped or damaged, and replace it if needed.

How to Choose the Right Replacement String for Your Dewalt Model

Not all trimmer string is created equal, and the right choice depends on what you’re cutting, how often you use your weed eater, and your model’s power. Below is a comparison of the most common string types to help you pick the best option:

For most homeowners, 0.080-inch round string is more than sufficient for weekly lawn maintenance. If you have a larger yard with thicker weeds or overgrown areas, opt for 0.095-inch square string for better cutting power. For commercial landscapers or users who regularly clear dense brush, 0.105-inch serrated string will hold up to heavy use. Always check your model’s manual for the recommended maximum string diameter to avoid overloading the motor.

Best Practices to Extend Your Weed Eater String’s Lifespan

With proper care, your replacement string can last 2 to 4 times longer than it would with casual use. Follow these tips to get the most out of your string and your tool:

• Avoid cutting hard objects: Never hit rocks, concrete, metal fences, or tree trunks with the string. This will cause it to break instantly and can damage the trimmer head’s internal components.
• Cut in multiple passes for thick growth: Forcing the string through dense, tough weeds or brush puts excessive strain on it. Mow the area first, then use the weed eater for edging and light touch-ups, cutting thick growth in 2 to 3 shallow passes instead of one deep pass.
• Clean the trimmer head after each use: Wipe off grass, mud, and debris from the trimmer head and spool after every use. Built-up debris can cause the string to jam or wear unevenly.
• Store string properly: Keep unused string in a cool, dry place away from direct sunlight. UV exposure breaks down the plastic in trimmer string over time, making it brittle and prone to breakage.
• Lubricate the string before winding: Coating the string with a small amount of silicone spray before winding reduces friction inside the spool, helping it feed more smoothly and reducing wear.

Frequently Asked Questions

How often do I need to change my Dewalt weed eater string?

It depends on how often you use the tool and what you’re cutting. For light residential use (1 to 2 times per month cutting grass and small weeds), you’ll need to replace the string every 3 to 6 months. For heavier use (weekly mowing and edging, or cutting thick brush), plan to replace it every 1 to 2 months. If the string is frayed, broken, or not cutting effectively, replace it immediately regardless of how long it’s been installed.

Can I reuse old string from a broken spool?

Yes, if the old string is not frayed, brittle, or nicked, you can wind it back onto a new spool. However, if the string has been exposed to UV light for more than 6 months, or has visible damage, it’s better to use new string to avoid breakage during use.

Do I need to wind the string myself, or can I buy pre-wound spools?

You can do either. Pre-wound spools are more convenient and save time, especially if you replace the string frequently. They are compatible with most Dewalt quick-load models and are a great option for beginners. Winding your own string is cheaper, as bulk string costs $0.05 to $0.10 per foot compared to $5 to $10 per pre-wound spool.

Why does my new string keep breaking right after installation?

This is almost always caused by one of three issues: 1) You wound the string in the wrong direction, causing it to tangle and jam when the trimmer is running. 2) You used string that’s too thick for your model, overloading the motor. 3) The string is overlapping in the spool, creating weak spots. Double-check the winding direction, string diameter, and make sure you wind it evenly without overlapping.

Can I use third-party replacement string for my Dewalt weed eater?

Yes, as long as the string is the correct diameter and length for your model, third-party string works perfectly. Avoid very cheap, low-quality string, as it breaks easily and may not feed correctly. Dewalt OEM string is optimized for their models, but reputable third-party brands are a cost-effective alternative that performs just as well for most users.

What size string does my Dewalt weed eater use?

Most 20V MAX residential Dewalt weed eaters use 0.080-inch (2.0mm) diameter string, while 40V MAX and commercial models use 0.095-inch (2.4mm) or 0.105-inch (2.6mm) string. You can find the recommended size printed on a label on the trimmer head, or in your model’s user manual.

Conclusion

Learning How to Change a Dewalt Weed Eater String? is one of the easiest and most cost-effective maintenance tasks you can do for your yard tools. With just a few basic tools and 10 minutes of your time, you can avoid costly repair trips and keep your weed eater working at peak performance all season long. Follow the steps in this guide, choose the right string for your model, and implement the best practices we shared to extend the life of your string and your tool. If you run into model-specific issues, refer to your Dewalt user manual or contact their customer support team for additional guidance. With regular maintenance, your Dewalt weed eater will tackle even the toughest yard work for years to come.