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Primary dangers
A brushcutter has a metal blade that spins typically at about 20,000 RPM. The potential for injury should be obvious. My machine can slice through inch-thick saplings without even slowing down, so what it would do to a person's leg hardly bears thinking about. But the most common injuries, I believe, are caused by objects thrown back at the operator by the blade.Secondary dangers
Brushcutters are very loud, and often used for long, uninterrupted periods of time. Hearing damage is therefore a real possibility.Safety tips
Use protective clothing, etcHearing protection is essential, as is eye protection. Most operators use goggles or safety glasses and a wire-mesh mask visor. I prefer safety glasses to goggles, because they don't steam up. Goggles or glasses will protect your eyes, but they won't protect the sensitive skin around your eyes, which is why a visor is important. When objects are thrown back by the blade, they really sting. Trust me on this. They will mostly strike your lower legs; wearing shorts, therefore, is not to be recommended. In fact, my personal preference is ensure that as much of my skin as possible is covered. I even turn my shirt collar up. Stout trousers will take the sting out of most of blade-thrown missiles, and most operators don't wear additional leg protection. However, some operators like to wear shin guards. A heavy shirt is sufficient, in my experience, to protect against objects being thrown at torso height (but if you're working around, say, broken glass or fragments of metal, you might want something stouter). Protective clothing is important, not just to guard against thrown objects, but because if you're working in the thick of brambly undergrowth, you're going to get tangled up in it eventually -- I always do, anyway. Use a shoulder harness (if you have one)
A powerful brushcutter is heavy and unweildy. Most machines of this type are supplied with a shoulder harness which, when properly adjusted, puts the weight of the machine on the operator's back, and not the arms. Adjustment is critical, and takes a bit of time. Ideally, the harness should place the brushcutter at such a height that, when you're standing upright, the cutting head is an inch or so above the ground. Incorrectly adjusted, the hardness just gets in the way. Remember that the blade will spin for some time after the engine stops
Heavy-duty, petrol-engined brushcutters usually have a clutch to prevent damage to the engine if the blade snags. This means that the blade will continue to spin for some time after the engine is shut off. A heavy steel blade spinning at 20,000 RPM has a lot of momentum, and will take up to a minute to come to a complete standstill. Exercise caution when untangling the blade
However careful you are, it's likely that material will get tangled in the blade from time to time. If the blades are sharp (they aren't always -- some machines have blunt blades and rely on the momentum to cut) the need for caution is obvious. But you should also be aware that hot petrol engines do occasionally turn over spontaneously, so you should switch off, or remove the spark plug lead, or whatever your machine requires to disable the engine. Ensure that the blades do not spin at tick-over
The blades of a properly-adjusted petrol brushcutter should not spin when the engine is at idle. If they do, it makes the machine very difficult to handle safely. If the engine idles too fast, the blades may spin even when the throttle is not depressed. Over-fast idling may be the result of incorrect carburettor adjustment, but a more common problem is an incorrect fuel-oil mix in two-stroke engines.
Getting good results
Allow the blade to come to full speedWhen the clutch is engaged, it will take a while -- perhaps ten seconds -- for the blade to spin up to full speed. It won't cut properly if it isn't running at full speed, and will tend to snag. Know what the machine is capable of
This is most important -- a bruchcutter is really suitable only for cutting material that is well anchored -- usually in the soil. If you're facing a chest-high wall of bramble, it's tempting to think that you can just swing the brushcutter around and pulverise it. But this doesn't really work -- the bramble just gets pushed around, and most likely tangles up in the blade. In practice, a brushcutter is really only effective at cutting growing material at its roots, where it can't get out of the way of the blades. In any case, waving it around at chest height is not ideal from a safety perspective, to say the least. Sometimes really dense bramble can be tackled by pushing the brushcutter under the mass of vegetation and slicing off the bramble from the roots. You should then be able to drag the rest out with a rake, if you're lucky.
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