This article was originally published on the web at cranbrookengineering.co.uk however that website is defunct at April 2013. The copyright is with the original owners of cranbrookengineering.co.uk
The types of hedgecutter and hedgetrimmer:
Manufacturers are not consistent in their use of the terms 'hedge trimmer' and 'hedge cutter', though some would say that the latter are bigger beasts, for example with wider tooth spacing (or the ones attached to tractors). We are here discussing hand-held tools with two blades 'scissoring' across each other, and will call them 'hedge trimmers'.
Most people know that you can get hedgetrimmers with teeth on both sides or just one side. But why? The best type for all-round use is the double-sided variety. You use it in sweeping arcs in either direction, and it is equally good for right or left handers.
Single-sided machines are used (often by contractors) because they are invariably rather long and so cut a lot in one pass. They are lighter than their double-sided brothers, length for length. And they are wielded in a kind of pushing motion. This type of machine often has a collector, to guide the clippings into 'drifts' and help them to fall where they are quicker to pick up.
Some long-reach hedgetrimmers have adjustable cutting heads so the angle can be adjusted. They are meant to allow you to trim tall hedges without ladders or a tower. But they are tiring and difficult to use accurately, and they have the disadvantage that any clippings on top of the hedge will stay there and be impossible to collect. Long-reach hedgetrimmers are pretty useful for getting at bushes buried in a big shrubbery, but great care is needed to avoid cutting the wrong plant.
Tooth pitch can be wide for cutting coarse wood or narrow for more precise trimming of finer material. Each can be found on double or single-sided machines. The speed of reciprocation is often optimised to match tooth spacing: perhaps 3000 strokes per minute for coarse cutting and 5000 strokes per minute for ones meant to give a fine finish.
Low vibration and noise are important for operator comfort. Good hedgetrimmers have vibration damping in the design. Noise emanating from an engine sometimes within 20cm of your ear can be highly damaging, so ear protectors must always be worn. Safety is an important consideration with hedgetrimmers. First, always wear ear defenders; second, wear goggles and gloves. A helmet is also advised. Obviously it is dangerous to put your fingers anywhere near the blades while the engine is running, even at idle. Never use a mains electric hedgetrimmer without a safety trip inserted in the 13-amp socket: that way you will not be electrocuted if you accidentally cut the cable.
Hedgetrimmers can soon tire you out as they have to be hefted to strange positions and heights, which is one reason that most of them use light, two-stroke engines. Honda, however, have a tiny four-stroke which can cope with being tilted to any angle by using a dry-sump lubrication system. Two-strokes used to be considered hard to start, but really that is not true any more. But they do involve you in having to carefully mix the recommended ratio of two-stroke oil with unleaded petrol. Many machines come with mixing bottles to make that easier; or manufacturers like Stihl sell their oil in capsules, assuring you of exact quantities.
Electric motors are cheaper to buy and maintain, and they need no clutch - you just switch them on. On the other hand, they are not as powerful as petrol engines and they have the annoyance of a trailing mains lead. The way round that is to choose a cordless rechargeable model, perhaps also buying a spare battery. Batteries now tend to be lead-acid or Lithium-Polymer, which last well and which do not have the 'memory' problem of Nickel-Cadmium.
All the better garden machines have a good finish and a solid feel. Quality in a hedgetrimmer is chiefly to do with the blades and the anti-vibration measures. The best blades are drop forged and adequately thick. Spares are extremely expensive. Cheapo blades are stamped from steel sheet. Good machines have dual-reciprocating blades: both top and bottom blade are moved back and forth with cams. This reduces vibration, but there should also be other sophisticated anti-vibration measures. The manual will say how much vibration is experienced at each handle.
Ideally the clutch should slip if the blades jam in use on a thick branch or worse, preventing breakage. Controls should be easy and comfortable and the rear handle twists on some machines to allow you to approach the work at various angles. The best long-reach machines have heads which are infinitely adjustable over a wide range rather than in coarse steps of 45 degrees.
All hedgetrimmers come with maintenance instructions, but 'once a year' is a good rule for most people. Sharpen the blades with a file and set them so that they are snugly together but cannot possibly jam. It is skilled work, probably best left to a professional. Electric machines need less maintenance and are therefore cheaper to run than petrol models; but sharpening them is still a tricky job.
Keep the air filter of engines clean: a dirty one causes wear. Be careful to mix the fuel up correctly, and give the hedgetrimmer a shake before using it, to ensure mixing of the petrol and oil. It is a great mistake to keep old fuel as it goes stale within a few months, making starting difficult and gumming up your carburettor. This can be avoided by adding a little fuel preservative, such as Briggs & Stratton make.