Tooth pitch
The distance between the individual teeth of the shrub attachment (see "Tips") supplied with the tool. The
larger the pitch of the teeth, the easier the tool will cope with thick branches, however, the quality of the work will be quite rough. Conversely, more densely spaced teeth work "cleaner" but are less suited to tough conditions and large branches.
Power
Hedge trimmer motor power expressed in watts.
The performance of the tool primarily depends on the engine power, and this concept includes both the overall speed of work and the ability to cope with difficult tasks like cutting thick branches. Therefore, when choosing, it is necessary to take into account both the general volumes of the planned work and the material with which you will have to deal. For example, a powerful hedge trimmer may be needed even if it is only a few metres of hedge — if the branches in this hedge are quite thick. On the other hand, "more powerful" does not always mean "better" — after all, this parameter affects the weight, energy consumption (or fuel consumption) and the price of the tool.
If we talk about specific numbers, then the optimal power for most household tasks will be about 400-600 watts. Battery models (see "Power"), designed for small amounts of work in simple conditions, may have less power, and in gasoline models (see ibid.), on the contrary, it can reach 900 – 1000 watts.
In addition to watts, power can also be expressed in horsepower; this designation is traditionally used in gasoline engines. 1 HP approximately equal to 735 watts.
Power
Hedge trimmer engine power expressed in horsepower. For more information about the value of power in general, as well as the ratio of horsepower and another unit of power — watts — see the “Power” paragraph above. Here we note that such a designation is typical mainly for models with gasoline engines (see "Power").
Stroke frequency
The frequency of movement of the teeth in bush or grass attachments (see "Tips"). The design of most of these tools is such that for one revolution of the engine, the teeth make one complete cycle of movement back and forth; therefore, the stroke rate is usually determined by the speed of rotation of the engine and is indicated in revolutions per minute.
It is believed that the quality of the tool’s work largely depends on this parameter: the more often the stroke, the cleaner the cut will be. Ratings up to 2200 rpm are usually typical for entry-level devices, up to 2800 rpm are average, and advanced models can have speeds of 3400 rpm and even higher.
Rotary handle
The rotary handle allows to carry out a cut from the most convenient position for the operator. It provides a comfortable grip on the tool to perform a specific cut. Usually, the position of the
rotary handle is adjusted by rotating around its axis.
Engine size
The working volume of the petrol engine installed in the hedge trimmer (if equipped, see "Power"). Usually, the larger the volume, the higher the engine power (see above). On the other hand, power is usually directly indicated by the manufacturer, and besides, it depends not only on this parameter, but also on a number of other factors. Therefore, in fact, volume is usually a secondary indicator, allowing to some extent to assess the economy of a brush cutter: for equal power, a larger engine is likely to have a higher fuel consumption.
Fuel tank volume
The volume of the fuel tank installed in the brush cutter with a petrol engine (see "Power").
The larger the tank, the more fuel can fit in it — the longer the unit can work without refueling. And knowing the approximate fuel consumption, by the volume of the tank, you can also estimate the approximate time of work on a single refill. At the same time, brush cutters rarely have to work without interruption for a long time, refueling, usually, does not cause any particular difficulties (if there is a supply of fuel, but this supply is not difficult to provide); in addition, a volumetric tank would have a noticeable effect on the dimensions of the unit, and in a filled state, also on its weight. The latter is especially critical, given that the instrument is supposed to be “carried around”. In light of all this, the tanks of modern brush cutters are made small — usually about 0.5 liters or even less.
Noise level
Approximate noise level produced by the hedge trimmer in normal operation. This parameter allows you to evaluate how comfortable it will be to work with the tool: the lower the noise level, the less discomfort it causes for the operator and others, and the lower the likelihood that special hearing protection will be needed during operation. At the same time, note that loud noise is an inevitable side effect of high power — it would be too expensive and difficult to make a powerful and low-noise tool. In addition, this figure is only approximate. Firstly, different manufacturers may indicate it differently: for idling, for full speed, for half power, etc. Secondly, the actual volume of work may also differ from the claimed one due to the peculiarities of a particular situation: for example, working with thick branches leads to an increase in the load on the engine, which can also affect the noise level.
Another specific point is that the decibel used to measure this indicator is a non-linear value: an increase of 1 dB corresponds to an increase of 1.26 times, 3 dB — 2 times, etc. Therefore, to assess the loudness of work, it is easiest to use comparative tables. Here is one of the simplified versions of such a table for the range in which most modern hedge trimmers work:
65 dB — loud conversation at a distance of a metre;
70 dB — loud conversation of several people at the same distance;
75 dB — shout from the same distance;
80 dB — the ringin...g of a mechanical alarm clock, a loud cry at a distance of 1 m;
85 dB — loud screams at a distance of 1 m;
90 dB — heavy truck or freight car at a distance of 7 m;
95 dB — subway car at a distance of 7 m;
100 dB — noisy industrial shop.
