A Stihl trimmer and brush cutter comes with a head that mounts the cutting blade. This blade can be unscrewed, detached and replaced with a different blade. Blades will dull and chip over time, requiring you to replace them. You can also swap the blade on your trimmer for a different style that suits a different cutting job. Stihl must certify all replacement blades, as other types will not work properly and may be dangerous. Always wear work gloves when removing and replacing the metal cutting blades.
Lay the Stihl trimmer on flat ground. Lay the unit so the head is pointing up. Put work gloves on. Unscrew the mounting nut clockwise in the centre of the head with a wrench.
Lift the rider plate and thrust washer off the metal blade. Lift the blade off the output shaft. Discard the old blade, but keep the rider plate and thrust washer if they aren't cracked or damaged.
Set the new trimmer blade onto the output shaft and thrust plate. Set the thrust washer and rider plate on top of the metal blade.
Hold the thrust plate and blade to keep them from spinning. Screw the mounting nut on counterclockwise. Tighten the nut fully with a wrench.