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Brush cutters must deal with a wide range of vegetation. Here I’m going to go through which are the best STIHL Brush cutter replacement blades. They will get you through the job quickly and effortlessly.
Brush cutting is a difficult combination. There’s grass, soft and short that a line will sort out in no time. Then there is the tufted tougher grass, the one that wraps itself around the line and stops the machine. So, we haul out the blade, but which one is the best for the job.
The short answer is that it depends on the dominant type of vegetation that needs to be cut.
There are a host of blades available, and they all fall into four categories. Knives, Chisels, mulching, and smasher blades. We will concentrate on the first two categories.
Before we do let’s have a look at some basic brush cutter skills.
It’s all in the Swing of the Blade
The periphery of a Brushcutter blade moves astonishingly fast. Bear with me for a minute and let’s consider just how fast.
Why is this so important? Well because of the speed only a small fraction of the blade is going to do any cutting.
A conventional blade of around two hundred millimeters diameter has a circumference of around three hundred and forty millimeters. If we take the average brush cutter blade turning at around 3,000 RPM (that makes the math easier) it means that an individual tooth on the periphery of the blade is passing the same point fifty times a second.
That’s why swinging the brush cutter from side to side results in a far quicker rate of cut. The individual teeth are being exposed to more grass in a given time period.
The swing of the blade head also prevents the cut grass from falling onto the head and choking the blade.
The range of blades stretches from a two-blade knife all the way up to a forty-two-tooth blade (and sometimes beyond that). It becomes evident that the size and number of teeth have a huge impact on the performance of the blade.
Let’s make a start with the easy stuff
The soft short grass that the lawnmower can’t quite get to. The grass is generally of the same length and fairly short. Something that a line will cut without too much trouble. So, will a blade but the line has an advantage in that it can handle obstructions better than the blade. Cutting along a fence line is one area where the line has a big advantage.
The line hitting up to a rock or a pipe while cutting is of little consequence. It may well wear out the line a little quicker, but it is far less severe than a blade bouncing off a rock.
The realm of the knife Blades
As soon as I find the line beginning to struggle with longer tufts, I switch to a blade. Here there are a couple of options. The range starts with the two-blade grass cutting blade and moves through the three-blade star-shaped blade Then we have the four-blade cutter.
I found that the three-knife star-shaped blade combined the best of both worlds. It will cut the short and easy stuff quickly, but it will also slice through annoying weeds and tougher vegetation. Saplings of less than an inch diameter will be easy pickings for this blade. STIHL refers to these blades either as a Bush Knife Blade or sometimes as a Brush Knife Blade. Be aware that they do come in two sizes so check that your brush cutter can handle the size of blade you are getting.
I have used this type of blade for many years and for me the great advantage is that you can flip the blade. This allows the use of the alternative sharpened edge. Sharpening the blade is also easy and quick and can be done with a normal flat file.
There is also a range of blades that are referred to as metal grass blades and these look like circular saw blades with few teeth. Typically, they will have six or eight teeth.
They will cut both grass and brush but tend to be better with the latter. The one drawback that they have is that they are unidirectional. You can’t flip the blade and you will have to sharpen each tooth. A lengthy process compared to sharpening the Bush Knife Blade.
So, for the easier jobs where the line begins to struggle my vote goes to the STIHL 250 mm Bush Knife Blade.
Moving on to tougher tasks
Here we are talking about brush clearing as opposed to grass cutting. These are areas where the grass has got away and is over knee height. To add a little adventure there will be saplings and young trees hiding in the long grass together with a rock or two.
The problem here is that as cutting progresses the long grass, weeds and saplings are going to fall onto the head of the brush cutter. This is going to result in the three-bladed Brush Knife getting choked. Added to this the longer tufts will carefully wrap themselves around the blade and force you to stop and clean the head.
In situations where there is a fair number of small saplings of up to three-inch diameter to get through a different approach is required.
Chisel blades seem to be the answer. These are blades that are very similar in appearance to circular saw blades. There are a wide range of teeth configurations to choose from and they all have different features.
Let’s deal with the number of teeth, to begin with. Here the adage of less is more applies. The reason is that the brush cutter shaft is too long. It won’t allow for the necessary force required to guide a large number of teeth through a three-inch diameter trunk.
The result is that instead of the blade moving through the wood quickly it is going to heat up. Eventually, the brazing holding the teeth is going to melt and that is the end of the blade.
To overcome these operators, tend to swing the blade head into thicker saplings. Hoping that the speed of the swing is going to get the blade through the wood. This places enormous strain on the drive shaft of the machine and will result in severe wear on the machine.
Thicker saplings of over three-inch diameter are also going to encourage the blade to kick out of the cut. This makes controlling the machine problematic.
The solution, and it is not a perfect one, is a compromise using a blade with fewer teeth.
Blades with tungsten carbide teeth are going to last a lot longer. They are also going to be very difficult for the average owner to sharpen. Tungsten Carbide blades need Special diamond files to sharpen these teeth.
Steel blades are easier to sharpen especially those with chainsaw blade profile teeth. They also get blunt a lot quicker.
The STIHL Grass Cutting Blade is available in four or eight tooth models. This blade is the one I would go to if heavy grass and saplings of up to two-inch diameter dominate the vegetation.
This blade gets my vote because of its versatility. It can deal with tangled weed and stubborn tufts as well as small saplings. I would go for the four tooth version if I had the choice.
With a regular swing rhythm, the cut vegetation won’t fall on the blade. This allows a quick movement through tangled undergrowth.
Although the blade is not reversible it is easy to sharpen with a conventional file.
The three-knife star-shaped blade and the four tooth blade are almost interchangeable. The star-shaped blade is quicker through the easy stuff and the four tooth blade is better at the heavier material.
The vegetation that you are dealing with is going to be the deciding factor.
What to do about small trees and thicker growth
Having got through most of the cutting the more difficult two and a half inch and bigger stems are left. There is a whole range of blades all claiming to zip through these without a problem. Yes, they may do so for a brief time before the edge is blunted, and then it becomes laborious.
Just to add to the problem you are going to be cutting close to the ground. Dust and dirt are going to play havoc with the cutting edge. The blade will be blunt in a very short space of time.
Cutting a couple of inches above the ground will get you out of this problem. However, then there will be a whole lot of little stumps perfectly positioned to trip you up.
So, what is the best replacement Blade?
The very short answer is that there isn’t a blade that will be all things to everyone. It’s a bit like asking which four by four is best for country and city driving. It is a compromise. So, I am going to suggest two blades.
They have both served me well over many years. Changing the blade to suit the conditions will save you time and a lot of wear on both the machine and the blade.
STIHL Three-Knife Brush Knife Steel Blade
For the easy stuff go for the three-knife star-shaped blade. STIHL refers to this blade both as a ‘Bush’ and the ‘Brush’ cutter. They come in two sizes so be sure if you go for the bigger blade that your machine can accept it. I sharpen these blades on a small bench grinder, but you can use a hand file as well.
This tri-bladed steel brush cutting attachment is designed for brushcutters to cut through heavy grass, reeds and light scrub. This tri-bladed steel brush cutting attachment is designed for brushcutters to cut through heavy grass, reeds and light scrub. 
STIHL Grass 8 Steel Blade
For the heavier stuff, the Four or Eight Tooth Grass blade has given me excellent service over the years. It won’t be as quick through the easy grasses as the star-shaped blade, but it will get through the smaller saplings a lot quicker. A bonus is that it is far less jarring on the operator and the machine.
Stihl 4001 - 713 - 3803 - 25.4 millimeter sheet metal has 8 teeth and is made of steel. This grass-8 blade is for cutting thick dry weeds and rushes.
FAQs
Question: What about mulching Blades?
Answer: Mulching blades are two or three knifed blades with the end turned down. They perform well in removing small bushes and shrub-like vegetation. It is difficult to cut grass with them because of the downturned edges.
The mulching blade requires a different cutting action. With this blade, you need to cut in a downward arc. From the top of the shrub or bush towards the ground. It is a tiring exercise.
Unless the area you want to clear consists entirely of small bushes and shrubs, you will be better served with the four or eight tooth Grass Blade.
Question: How often should I sharpen brush blades?
Answer: A lot depends on the vegetation that requires cutting. Generally, I found that sharpening the blade every time I refill the gas tank is a good practice. For blades that can be flipped like the three-knife star-shaped blade, you can get away with sharpening every second fill. Unidirectional blades need re-sharpening when the gas tank is empty.
Question: Do brush cutter blades need extra maintenance?
Answer: Apart from keeping the blade sharp, there is no additional maintenance required. However, after hitting a solid obstruction like rock be careful about checking the blade to avoid potentially serious injury. Remember this is a seriously fast-moving piece of equipment and it can cause substantial damage.
Using a blade does result in additional wear on the head of the brush cutter. To avoid any damage, it is a good practice to fill up the grease port after refilling the gas tank.
Question: Can I trim small branches with the brush cutter blade?
Answer: There are a whole lot of videos showing brush cutters happily loping off small branches from trees. It is tempting to get to branches higher up than you can normally reach but the brush cutter isn’t designed for this type of work.
Brush cutter blades with chainsaw teeth are the most appropriate for this. But because of the high risk of the blade kicking out it is a practice best avoided.
Question: What about Smasher Blades?
Answer: Smasher blades have pivoting sections that spin out as a result of the centrifugal force.
They rely on the speed of rotation to smash their way through the vegetation. Quite honestly, I have never used one and would hesitate to try.
Blades with sharp knives are far more efficient.
Conclusion
There are a lot of brush blades available and the vast majority are good. What makes me choose the two STIHL blades is that they suit the environment I work in and that should be your criteria as well. I also find that the seasons tend to alter my selection. In summer when the vegetation is soft and growing, I use a line. In winter a blade is more efficient with the dryer, more brittle vegetation.
STIHL blades have been my choice over the years because their quality is superb and price-wise they are competitive.
The most important aspect of blade selection is the environment it has to perform in. Whichever blade is chosen the most important factor that determines its efficiency is the maintenance of a sharp edge.
Blades that are kept sharp make the job a whole lot easier both for the operator and the machine. Never hesitate to sharpen the blade. It will always reward you with an easier cutting operation.