Welcome to the ultimate guide for anyone ready to get more from their string trimmer with the right brush cutter blade. Tired of dealing with stubborn saplings, tall weeds, or thick patches of brush that laugh at plastic string? Swapping out that bump feed head for a heavy-duty metal blade can take your cutting power to new heights. Today, you’ll see what five of Stihl’s top steel brush cutter blades can do—and which ones will truly give your yard or land the edge it needs.

No more guessing which blade fits your job. This post covers everything from blade design and safe installation to in-depth testing results. By the end, you’ll know exactly which brush cutter blade is right for your tasks.

String trimmer blades come in a range of shapes and cutting teeth. Stihl’s top five blades each have a specialty, so picking the right one depends on the job you want done. Here’s a quick overview:

• Grass Cut Blade (Multi-directional) – Double-edged, works both ways, for general grass cutting
• Grass Cut Blade (Single direction) – Fixed direction, fast sweeping in heavy grass
• Brush Cut Blade (Brush Knife) – Tough, two-sided, handles thick grass and brush
• Wood Cut Blade (Chisel Tooth) – Chainsaw-like teeth for saplings and small trees
• Wood Cut Blade (Scratcher Tooth) – Aggressive teeth, bites into hardwoods

Let’s break down what each blade is built for, what makes them unique, and how they mount up.

Some blades can be used on both sides (multi-directional), while others must be used in one direction, shown by an arrow on the blade. This matters because using the wrong direction can reduce cutting power or even be unsafe.

Here’s the breakdown:

• Multi-directional (double-edged):

  • Can use both sides, flip the blade when one side dulls
  • Usually found on the Grass Cut (multi) and Brush Cut blades

• Single-direction (one-sided):

  • Must be mounted according to the arrow
  • Stihl logo should face up and readable when installed

Mounting details:

• Seat the blade on the trimmer’s collar
• Attach the splined washer (it has teeth that fit the collar)
• Add the protective donut to save the threads
• Lock down with the nut (left-hand thread—turn left to tighten, right to loosen)

If a blade seems wobbly or vibrates, take it apart and check seating. A crooked blade will cause harsh vibration and won’t cut right.

Switching from a line head to a metal blade isn’t tricky, but paying close attention keeps you safe and protects your trimmer. Here’s how to get it done right:

You’ll need:

• A locking tool or screwdriver
• Stihl scrunch tool or wrench

Installation steps:

1. Lock the shaft: Slip a screwdriver or locking tool into the hole on the trimmer head to lock the shaft in place.
2. Remove the bump head: Remember, it’s a left-hand thread. Turn to the right (clockwise) to loosen and remove.
3. Set the blade in place: Place it over the collar—check to see it sits flat and where it should.
4. Place the splined washer: The washer gears mesh with the collar. Push it down firmly.
5. Add the protective donut: This guards the threads from damage.
6. Tighten with the nut: Turn left (counterclockwise) to tighten.
7. Double-check alignment and tightness before you run.

Warning: If the blade vibrates or wobbles during use, stop and check installation. Proper fit is key for cutting performance and safety.

Running a spinning metal blade inches from your body is no joke. A string might smack your shins—these blades are a different story. Level up your gear and habits before you start.

Recommended safety gear includes:

• Sturdy boots and long pants (or steel’s full-leg chaperone apron)
• Ear protection and eye guard combo , ideally with a metal mesh visor
• Upgraded guard: Larger brush guard or woodcut guard with limit stop (to shield you from debris and block dangerous parts of the blade)

Key safety tips:

• Never use shorts or open shoes—flying objects or contact can injure quickly
• Make sure your blade guard suits the blade you’re using
• For woodcutting blades, always switch to a “limit stop” guard if possible. It blocks part of the saw for added safety

Working with metal blades comes with more risk. Take your time and be prepared with the right gear and setup. 

All field tests used the  Stihl FS 131 R gas-powered string trimmer , known for its high-torque engine and robust build. Each blade was run through grass, brush, and wood to see how it really performs in the wild.

• Grass: Delivers a clean, flat cut. Not much faster than string overall, but it does a neat job. Needs fewer stops to service, since there’s no string to replace.
• Thick grass: Handles thicker patches better than string. Can tangle in brush if pushed hard.
• Pros: Long-lasting edge, no bumping or string changes needed
• Cons: Not much faster than string, can slow down in brushy areas

• Standard, tough grass: Noticeably smoother and faster than the first grass blade. Keeps engine speed high, lets you move at a faster pace.
• Brush: Does cut small brush or bushes, but quickly reaches its limit. Burning smell and loss of edge can result from going past ideal size.
• Pros: Cuts fast, stays sharp longer in grass
• Cons: Loses effectiveness and paint in denser brush

• Grass: Excellent performance, almost as good as the grass blades.
• Brush: Shines in thumb-sized brush and tough, vine-covered patches where string trimmer heads would fail.
• Value: It’s the top seller for a reason—handles a wide range, from grass to hardy brush. Costs more, but offers the best combination for most tasks.
• Pros: Versatile, long life (can flip for double use), efficient, handles brush up to thumb size well
• Cons: Struggles with anything thicker than about thumb-size wood

• Grass: Cuts, but it’s not optimal. Switching to a grass blade is better if cutting lots of grass.
• Wood: Carves through hard wood and trunks up to about three inches, almost “like a hot knife through butter.” Chainsaw-like teeth create real wood chips rather than just burning through.
• Limit: The donut washer physically limits depth, so you can only cut to a certain diameter (about three inches).
• Pros: The top pick for wood, best if clearing small trees. Fast, clean, little burning.
• Cons: Not great on grass. Requires guard with limit stop.

• Grass: Can cut, but it’s slow and drags, especially in thicker patches.
• Wood: Sharp, ragged teeth bite into hard wood. Best suited for smaller trunks. Tends to “slingshot” when cutting on the wrong side—safer to cut towards yourself on the left.
• Cut quality: Leaves more visible burning on dry wood, slower than the chisel tooth blade.
• Pros: Good for small, tough wood and brush.
• Cons: Prone to kickback or slingshot effect, slower cuts, stronger drag.

Testing each blade confirmed that no one tool fits every need, but two stood out:

1. Best all-purpose blade: The Brush Cut Knife Blade . It slices through heavy grass and brush up to thumb size with ease, making it ideal for yards with mixed growth.
2. Best for wood and thicker brush: The Wood Cut Blade (Chisel Tooth) . Nothing else chews through saplings and hardwood like this one. Pair it with a trimmer like the Stihl FS 131 R for the best performance.

If you regularly cut both grass and brush, consider picking up both the Brush Cut Knife and the Wood Cut Chisel Tooth blades. Always use the biggest, strongest trimmer your budget allows. It makes every blade more productive.

• Browse Stihl String Trimmers at Main Street Mower for everything from residential to commercial models.
• Find all the String Trimmer Accessories, including replacement blades and guards .
• Dive into more helpful and hands-on trimmer info, tips, and experiments in the full trimmer and blade educational playlist .

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