I'm looking at getting a decent petrol-powered strimmer for my large garden. I saw one that comes with interchangeable heads: line, rough-cut, and one more like a saw blade. The idea being they can cut thicker stuff from first to last.

Other strimmers just seem to come with line (2.5mm or so). I've no idea what a line can cut through before it just gives up?

  • Feel free to edit my question to ask this in a better way... As you say it will vary but i think you get what I'm trying to ask?
    – Mr. Boy
    Commented May 11, 2017 at 15:17

2 Answers 2


A gas powered line strimmer a word I've never heard to call what we call 'weed wackers' or line trimmer. Good for you! Gas is the best way to go for power. These are able to cut through 1/2" branches but not quickly and you have to 'bounce' the line tips off the branch. Giving it 'English', grins, what people do when playing pool? Quickly hitting the branch and pulling it backwards even faster. They are not made for this but the odd branch won't hurt this if you can keep that head spinning, not allowing it to slog down slowing the motor which can shorten the life of your motor.

I have 2 beloved tools that I won't go anywhere without; my line trimmer, a little Red Max I've had for 30 years and I got it from a pawn shop where it must've been at least a decade or two old...and a Stihl blower. Keep these machines CLEAN. Get extra filters for the air/carburetor and the gas filter. Keep the dirt out of your machine and it will last forever.

Use only petrol' without ethanol. This is a big deal. Use the best 2 cycle oil and make sure you actually measure the correct amount per gallon or liter. Don't just dump it into the petrol willy nilly like lots of people do.

The most important thing to know about is the head. Forget the 'bump and go' heads. ugh. I use a stationary head where you have to cut lengths of line, insert them into the head. Pull up the two ends to a point directly over the center of the head or wheel to nip off with your pruners/scissors. Making sure the two lengths are identical and the correct length is very important for your motor and your cutting capabilities. So the last step before you start 'weed wacking' is to find a concrete side walk or a boulder/large rock, turn your wacker upside down (it is turned on at this point) watch your down line (where the rotating heads will throw rocks at missile speeds to break windows, blind babies, that sort of thing) and lightly touch the ends of your spinning lines to the concrete or boulder. You will HEAR the sound of the motor change as the line lengths become perfect. The sound goes from low to high quickly. You'll learn to cut 4 or 5 at a time and loop through your belt loop for replacements. Also carry a pruner or scissors.

You always always wear safety glasses!! That 'shield' is worthless. I actually take mine off so that I can see where I am cutting. Using this machine is like doing surgery. You will learn to be able to cut exactly what you want as these machines can scalp a lawn sure as certain or ding up wood fences or girdle trees.

This machine is only for grass, grassy weeds, non woody weeds. Not for brush, small shrubs, never for hedging shrubs. You'll find that edging your lawn there is no better tool. Your line will get shorter and shorter as you work. Especially if trimming between concrete and grass, wacking weeds in cracks of the sidewalk, soil at the bottom of a trim will cause your line to have a shorter life...takes about 5 to 15 minutes working a residential landscape then you need to take out the ragged, too short piece of line and insert another chunk of line, pull up both ends of your line at the center of the outside of the head and snip the two lines. The length varies a bit from machine to machine but the best length to operate is about 4 to 5 inches...not 6". If the line is too long all it does is beat the grass or weeds to death and will possibly break to be uneven again. You'll have to pull the two lines up again and snip then turn upside down to hone the tips and make their lengths perfect. This 'upside down' position is also done with edging your lawn. The motor is up by your head and the head is down. The line acts like a blade this way. 'Honing' your lines makes your machine far more efficient and saves the wear and tear on your motor. The lines will be at their absolute most powerful rotation. Does that make sense? Every single time you switch out line you will do this. Cutting the chunks of line off the reel, you will find the perfect length so that you don't waste line but there is no way you'll be able to make the perfect length for the fastest most powerful rotation. You have to turn it upside down and lightly hit the concrete (watching watching watching your down line for windows, cars, pedestrians, babies and eyeballs) and again, you'll know when the lines are perfect by the sound of your motor. You'll hear the initial sound and then it will go up...as the line is made completely equal.

When you purchase (look at Stihl or Husqvarna spelling might be off), this is no time to by cheap 'home owner' type machines. When you use this guy you will love it so much you'll tend to overdo. You'll have the prettiest lawn edges around. Weeds will run from you, grins! I am able to use this to weed in between shrubs and perennials and flowers but I am quite good, snickers. I was thinking of going into competition, I am serious! Trimming the edges of lawns for instance with the machine in blade mode or upside down I could run backwards cutting only grass absolutely perfectly. Some guys did it going forward but going backward gave me the most control. Weird, I know.

I hope this helps. You will love this tool. Oh, when you get your new machine make those guys that sell it to you break it down, show you the filters, get replacement filters, purchase a reel of STAR shaped line (each head has it's own diameter and they are fairly common among different machines)...I've forgotten the number but they will show you the proper diameter. Get a bunch of premeasured 2 cycle oil, a dedicated gas tank for mixing. Get a 'stationary' head instead of the 'bump and go'...sounds so nice but NOT. The line never comes out at perfect lengths, the shield actually is used to 'cut' the lengths but when you get more proficient with weed wacking and edging you should get rid of the shield. You want to be able to see right where you are cutting. You'll have to be very wary of your down line at all times. That shield gives the false impression of safety. Make sure you get a couple of pairs of safety glasses. I liked the yellow. The shaded makes it too hard to see, my opinion. And safety glasses do look cool. Far better than an eye patch! I had 2 of my guys ruin an eye apiece. As the foreman I had to make them put their seatbelts on in the trucks, make sure they wore their glasses and ear protection. 2 guys at separate times went around the corner out of sight of the padrona or jeffa to take their glasses off! Then off to the emergency room, ruining our route timing (sorry we had a Hitler for a boss) and two weeks later another one did the same even after watching what his compadre had gone through. Sigh.

Another 'I told you so' moment only not so funny to see the world through one eye. Let me know if I can clarify anything. This is hard to show through words.


Stormy at a nice and generic answer. You must read it, but I complement it.

Your question is difficult to answer because you have the wrong assumption. I found the packet grass the most difficult thing to cut with trimmer, not the weeds with larger diameter.

You should care about the power of the string trimmers. A powerful trimmer can maintain constant velocity of the strings, so it can trim more dense things. For the size/diameter of string, it depends on what you trim. Note: like the wheel on cars, the size and weight matter. A less powerful trimmer cannot give enough (constant) speed to thick and long string. So power is important, than the thickness depends on how long the string should be (long: less trimming, but more pebbles (you will fell them on evening, on your legs).

There is disadvantages with power: larger so more weight (you will feel it at evening if you use it whole day), and it use more gas.

I have two trimmers and various heads:

  • the string head for normal use. I find not much difference on type of string, but on consumption (and thus lifetime)
  • a metallic head (form of a 4 edge star, so with "4 blades") for dense grass and weeds (but no woody or peddles/stones/rocks). This is much more speedy but also it could break if there is some stronger material
  • a saw like head (12 or 20 "blades"). I use this for woody things. Also this is delicate (so no stones around) and I feel that lack of power of my trimmer: it take time before it get full speed. I use it seldom

So I would recommend to buy a powerful string trimmer with a normal head, and when you find that you need more (and you have the right condition) you could buy some extra heads. Check that your trimmer allows extra heads (and BTW this is also an indication of having enough power).

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