How to Install a Steel Brush Cutter on a Line Trimmer

A blade turns your string trimmer into a tool that can clear gnarly brush.


Most string trimmer manufacturers supply attachments to convert the tool into a brush cutter. The most common attachment is a flat blade with three equidistant cutting arms, but some manufacturers supply cutters with teeth that resemble those on circular saw blades. While the exact procedure for converting the tool from a string trimmer to a brush cutter may depend on the model, it usually involves taking off the string head, replacing the deflector and attaching the blade. Once the blade is attached, the tool has significantly more ability to cause damage or injury and must be handled with care.


Lay the trimmer on a flat surface and disconnect the spark plug wire.


Block the drive shaft to prevent it from turning by inserting a rod into the hole just behind the trimmer head. A 1/4-inch hex wrench works well, or use the tool supplied with the trimmer for this purpose, if you still have it.


Turn the trimmer head clockwise to unscrew it. If a nut holds it onto the drive shaft, turn the nut clockwise with a socket wrench. Note that this is the opposite direction that you usually turn something to unscrew it. The trimmer shaft has reverse threads to prevent the cutter from loosening while the shaft is turning.


Remove the deflector. It may be screwed to the end of the shaft with Phillips screws or tightened to the shaft with a collar. Remove the screws or loosen the collar to detach the deflector.


Replace the deflector with the one supplied by the manufacturer for use with metal cutting blades. It should attach to the shaft in the same way as the one you removed.


Place the blade on the thrust plate of the drive shaft, fit the thrust washer over it and put the rider plate over that. The rider plate is shaped like the trimmer head and has a flat top that rides along the surface of the ground when you're using the cutter.


Place the nut on the shaft bolt and tighten it counterclockwise with a socket wrench. When you're finished, remove the blocking rod so that the blade can turn freely.

Things You Will Need

  • 1/4-inch hex wrench
  • Socket wrench
  • Phillips screwdriver


  • Brush cutter blades usually are symmetrical, so you don't have to pay attention to blade direction when installing one.


  • Wear goggles, gloves, safety shoes and protective clothing when operating a string trimmer with a brush-cutting blade.

Photo Credits

  • Thinkstock/Stockbyte/Getty Images
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