These three names get used for each other constantly, and shops rarely correct it. The machines do overlap, but they are built for different vegetation, and buying the wrong one usually means either a machine that stalls in thick growth or one that is too heavy for the job.
String trimmer
Cuts with a spinning nylon line. The line is flexible, so it cuts soft grass and weeds and does no damage if it touches a wall, a fence post or a tree trunk.
Best for lawn edges, boundaries, around obstacles and light weeds. It will not cut anything woody — the line simply wears away against a stem.
Grass cutter
In Indian usage this usually means a light machine with a metal blade, often two or three teeth, made for grass and soft weeds over open ground. It cuts faster than a string head and handles denser grass, but it is still a light-duty machine.
Best for lawns, field bunds, fodder cutting and general grass clearing.
Brush cutter
A heavier machine with a more powerful engine, a stronger shaft and a gearbox built to take load. It runs metal blades ranging from three-tooth grass blades up to multi-tooth circular saw blades that cut woody stems and small saplings.
Best for overgrown land, scrub, bush, thick weed, undergrowth in orchards and plantations, and anything with a woody stem. Most machines sold as brush cutters, including our petrol brush cutters, will also take a nylon head, so one machine covers both extremes by changing the attachment.
Side by side
- Soft grass, tight spaces, near walls — string trimmer or nylon head.
- Open grass, bunds, fodder — grass cutter or brush cutter with a grass blade.
- Dense weed, scrub, woody stems, saplings — brush cutter with a saw blade.
- Mixed work across a season — a brush cutter with two or three blade options is the most flexible single purchase.
Shaft, harness and how it actually feels to use
Two things decide whether a machine is comfortable over a long day, and neither appears in most specification tables.
Straight versus curved shaft. A straight shaft puts the cutting head further from your body, gives better reach under bushes and is the standard for brush cutting. A curved shaft is lighter and easier to swing for trimming work.
Side-pack versus backpack. A conventional machine carries the engine on the shaft with a shoulder harness. A backpack brush cutter moves the engine onto your back and drives the head through a flexible shaft, which shifts weight onto your hips and makes long sessions considerably easier. On sloping or terraced land the difference is significant.
There are also multi-function machines that accept a pole pruner, hedge trimmer or cultivator attachment on the same power head, which is worth considering if you have several small jobs rather than one big one.
Safety is not optional on any of them
A metal blade turning at speed will throw stones and cut through a boot. Every operator needs eye protection, ear protection, gloves, long trousers and closed boots. Keep the blade guard fitted — it is there to stop thrown debris, and removing it to fit a bigger blade is a serious mistake.
Keep other people at least fifteen metres away while cutting. Watch for blade thrust, which is the sudden sideways kick you get when the upper right quadrant of a spinning blade catches something solid. Cutting with the left side of the blade and moving right to left keeps thrust away from you.
Choosing on engine size
Engine displacement is a rough guide to what a machine will pull through. A small engine on light grass will work all day; the same engine forced through scrub will overheat, bog down and wear out early. If you are unsure, describe the thickest stem you need to cut and let that set the machine, not the price.
See the full brush cutter and grass cutting machine range to compare, and keep blades and spare parts on hand — blades are consumables, not permanent fittings.