Your grass trimmer will eventually need new mowing line installed to stay effective. Replace it quickly and easily with the help of our guide.

When the time comes to replace the line in your grass trimmer, you may face the question of deciding which type is best for your STIHL tool. The answer depends primarily on what tasks your trimmer needs to tackle. As a rule of thumb, the longer and denser the grass you are clearing, the thicker the trimmer line should be. This should also be taken into account when choosing the trimmer itself, because the thicker the line you use, the more power you need to achieve a clean cut. So tougher jobs require more power and a thicker line. To understand which trimmer line is appropriate for your needs, you should first consider the different mowing heads available at your local STIHL Dealer.

step-by-step guide to replace your trimmer wire:

1. Preparation

Switch the trimmer or brushcutter off. If using a petrol tool, remove the spark plug. If using a cordless trimmer, remove the battery or disconnect the connecting cable. Please check that the correct deflector approved for the blade and trimmer is fitted. Hold the grass trimmer upside down.

2. Lock the trimmer shaft

Insert a lock pin or Allen key into the hole in the gearbox. Turn the shaft until the lock pin clicks into place and the shaft is locked.

3. Remove the metal tool

Turn the nuts clockwise to loosen them. Then pull the blade and fastening components from the gearbox without removing the thrust plate. You can now replace it with a new one.

4. Replace with the new blade

Fit the replacement part onto the thrust plate; the thrust plate collar must fit into the bore of the metal cutting tool.

5. Fit the thrust washer and rider plate

Fit the thrust washer and rider plate onto the shaft. After changing the cutting tool, the pressure plate and running plate are placed on the shaft

6. Tighten the nut, Remove the lock pin

Tighten the nut by turning anti-clockwise using a combination socket tool. Replace any nuts with stripped threads. Now remove the tool that is locking the shaft.

Watch our walk through videos below:

How to replace trimmer line in your STIHL tool

STIHL offers a wide range of grass trimmers for domestic and professional use. These differ in various aspects such as power, drive type and handle type, as well as the mowing head supplied as standard. However, while the other characteristics mentioned are fixed, you can remove the heads installed on STIHL grass trimmers and replace them with alternative cutting tools. This makes them more versatile as you can tailor the tool to your task.

Different cutting tools need different processes: please choose the step-by-step videos to replace the line or polycut blades on your STIHL grass trimmer that suits you.

How to replace an AUTOCUT C 3-2 LINE SPOOL

It is really easy to renew the line as you work with an AutoCut head. Extending the twin cutting lines to the right length is simply a matter of tapping the mowing head on the ground while the motor is running. This action triggers a release mechanism which spools out some line; the length is then automatically adjusted by means of centrifugal force as the trimmer rotates.


How to replace an AUTOCUT C 3-2 MOWING LINE

Two-thread, for mowing and cleaning work. The mower line is automatically adjusted by tapping the mower head. The cutting line can be refilled from the outside without opening the housing. Housing with gripping contour for loosening and attaching the mower head by hand.


The white thermoplastic blades are also ideal for trimming around monuments and other solid objects as they don’t mark the stone. The blades are easy to change and some models can also be fitted with flexible nylon line in addition to or in place of the blades.


In summary, as well as being suited to different tasks, each type of head also requires a different procedure when it’s time to refill or entirely replace the trimmer line. Your trimmer head comes loaded with a spool of line which can be released a little at a time for use through several trimming tasks – but it won’t last forever. To replace it you can buy a new roll of line and refill your existing grass cutting head.

  • Wear appropriate protective clothing and follow the steps in the operating instructions for your trimmer
  • The wire spool must face upwards and the approved deflector for the wire and trimmer must be fitted
  • Lock the shaft with a lock pin or Allen key
  • To replace a wire: fit the new mowing head and tighten it while the shaft is locked
  • To replace a metal cutting tool: place the metal blade onto the thrust plate, fit the thrust washer and rider plate onto the shaft, and tighten the nut
  • Remove the tool and release the locked shaft

STIHL tip:

Prefer to use pre-lengthened sections of line rather than winding it on from a roll? STIHL DuroCut mowing heads are filled with pre-cut pieces of DuroCut trimmer line, supplied at the perfect size. DuroCut has a flexible core with a tough outer layer and blade teeth, enabling you to work with precision in taller, denser and slightly woody vegetation.

Not all heads are compatible with all tools. If you are not sure which heads are suitable for your grass trimmer, please ask your local STIHL Dealer for advice.