How to Change the Trimmer Head on a Troy-Bilt Weed Trimmer

Troy-Bilt offers multiple trimmer heads for its line of string trimmers, including the SpeedLock trimmer head. Also called cutting heads or bump heads, these parts tend to crack or wear out, even with normal use. Troy-Bilt trimmer heads are designed for easy, user-friendly removal and installation. In some cases, the only tools you might need are a flat-head screwdriver and/or a hex key.

If you want to attach the SpeedLock trimmer head, you only need to remove the bottom half of the current trimmer head. You can leave the upper portion of the cutting head on the shaft.

Notice that the bottom of the head consists of two circles: a larger circle with a smaller circular knob (the "bump knob") in the center. Look for tabs on the side of the larger circle and if you find them, push on the top tab with your thumb and depress the bottom tab with a flat-head screwdriver to release it. Repeat on all tabs until the large circle comes free and then push two additional tabs on the knob head. On models without tabs, push down on the larger circle while unscrewing the smaller circle until they both come free.

After removing the bottom half of the current trimmer head, remove the spring from the shaft. Next, place the SpeedLock trimmer head over the shaft so that the arrows on the SpeedLock point to the eyelets on the base. Place the spring back onto the shaft and then finish by screwing the bump knob over the spring. Push down on the bump knob while screwing it in place to ensure it threads properly onto the shaft.

To replace the entire trimmer head on your Troy-Bilt trimmer, start by looking for a hole in the shaft and/or on the spindle just above the shaft. If needed, rotate the trimmer head to align a second inner hole with the outer hole. Then, insert a hex key or small screwdriver through these holes to lock the trimmer head in place. This will allow the cutting head to unscrew from the shaft instead of spinning freely.

Note that some Troy-Bilt string trimmer heads have reverse threads; they unscrew clockwise instead of counterclockwise, so try both directions if you don't seem to make headway. Once the old head has come off, screw on the new one. Keep the hex key inserted in the lock hole until the trimmer head is hand-tight.

Not all cutting heads will work on a Troy-Bilt string trimmer. Before you purchase a replacement cutting head, verify that it's compatible with your string trimmer model. The packaging or online listing should have compatibility information readily available.

Follow simple safety precautions when working on your string trimmer. Because the head contains a spring that's under pressure, wear eye protection when disassembling the trim head. Never work on the trimmer while its engine is running. Disconnect the trimmer attachment from the engine to avoid any mishaps should the trimmer turn on unexpectedly.