Type
— Motobur. Traditional motor-drills are units of rather high power, designed primarily for drilling holes in the ground with the help of an auger — a characteristic rod with a spiral surface along the entire working length. At the same time, most motor-drills are designed for augers with a diameter of about 20–40 cm, and in the most powerful models, the maximum thickness of the drill can reach 60 cm. This makes it easy to drill wells for support poles, holes for planting trees and shrubs, etc. Units of this type can be quite heavy and require the participation of 2 people (see "Number of operators"). The predominant part of such devices uses internal combustion engines as power, however, there are
battery models and
electric drills.
—
Motor drill. In terms of the design of the cartridge, such tools are similar to the more common electric drills, and the same drills are used in power drills. The key difference is that instead of an electric motor, the rotation is provided by a petrol engine. This, on the one hand, allows you to achieve a higher torque than in an electric tool, despite the fact that the drill does not depend on sockets; on the other hand, the weight, dimensions and cost of power drills also turn out to be much larger. This type of tool is mainly designed for drilling where traditional electric drills are not suitable — for example, if high power is
...a decisive factor, or if there are no outlets nearby.Drive shaft diameter
The diameter of the drive shaft used in the drill (see "Type").
Working tools for motor drills — augers — are produced for a certain diameter of the drive shaft. Simply put, this parameter is, in fact, the size of the seat for the drill; compatibility with one or another auger depends on it. Most modern models use shafts with a diameter of 20 to 25 mm; usually, the larger the diameter of the shaft, the thicker the screw with which the tool is able to work.
ICE type
The type of internal combustion engine used in a power drill.
— 2-stroke. The main advantages of two-stroke engines, in comparison with four-stroke ones, are simplicity of design, low cost, as well as higher power per unit volume (as a result, smaller dimensions and weight). Among the shortcomings, it is worth noting a higher fuel consumption and noise level, as well as the need to prepare a gasoline-oil mixture for refueling. However, these shortcomings in this case cannot be called critical, due to which two-stroke engines are used in most modern motor-drills of all price categories.
— 4-stroke. Four-stroke engines are less noisy and more economical than two-stroke ones, and they need to be filled with gasoline and oil separately, which is much more convenient to use a mixture. On the other hand, they are more complex, heavier and more expensive, and therefore are rarely used, mainly in fairly advanced motor drills (although not necessarily high-power ones).
Engine size
The working volume of the motor-drill engine.
A larger volume (with the same type of internal combustion engine, see above), on the one hand, increases power, on the other hand, increases fuel consumption. However, in general, this parameter is a reference, and when choosing it is worth paying attention to more practically significant indicators — power, speed, gear ratio, etc.
Power
Engine power of the motor drill in horsepower. Horsepower is traditionally used to denote the power of internal combustion engines. 1 HP approximately equal to 735 watts.
Power is one of the key parameters for any motor auger: the higher it is, the higher torque can be achieved on the drive shaft, the thicker augers can be used with the unit and the better it is suitable for complex work and “heavy” soils. On the other hand, high power significantly affects the price, dimensions and weight of the engine. Therefore, manufacturers choose this parameter based on the price category and general purpose of the tool.
The most modest engines, about 0.8 – 1.5 hp, are installed in power drills (see "Type") — for such devices, high power is not needed, but light weight and compactness, on the contrary, are critical. For motor drills, indicators are 1.6 – 3 hp. correspond to the entry level, 3 – 5 hp. — medium, and in the most powerful models, motors of 7 – 8 hp are installed, which makes it possible to work with screws with a diameter of half a metre or more. At the same time, note that units of the same power may differ in screw diameter and other performance characteristics.
Power
Engine power of a motor drill in kilowatts. Watts (kilowatts) are a common unit of power, and this unit is also used for gasoline engines along with horsepower (see above).
Power is one of the key parameters for any motor auger: the
more powerful the engine, the higher torque can be achieved on the drive shaft, the thicker augers can be used with the unit and the better it is suitable for complex work and “heavy” soils. On the other hand, high power significantly affects the price, dimensions and weight of the engine. Therefore, manufacturers choose this parameter based on the price category and general purpose of the tool.
Indicators of 0.6 – 1.2 kW are typical for the most modest engines, these are mainly equipped with power drills (see "Type"). In entry-level motor drills, more powerful units are used, by 1.2 – 2.2 kW, the average class corresponds to an indicator of 2.3 – 3.7 kW, and in the most solid devices, the power can reach 5.5 – 6 kW. Note that units of the same power may differ in screw diameter and other performance characteristics.
Max. RPM
The highest speed that the engine of the motor-drill is capable of is, in fact, the speed of rotation of the shaft with the throttle squeezed out as much as possible.
The difference between idle (see above) and maximum speed determines the operating speed range of the engine. In this case, a faster motor will have less torque than a slower unit with the same power. At the same time, the speed of rotation of the drive shaft (and the torque on it) is affected not only by the engine speed, but also by the gear ratio of the gearbox (see above); this means that the use of appropriate gearboxes can equalize the capabilities of multi-speed motors. Therefore, it is worth comparing motor drills of similar power not by engine speed, but by the speed of rotation of the working shaft.
Fuel tank capacity
The volume of the fuel tank installed in the drill.
A larger tank allows you to work longer without refueling, but it significantly affects the weight of the tool. Given the peculiarities of the operation of motor drills, in fact it is easier to take breaks for refueling than to keep a large supply of fuel in the unit itself. Therefore, tank volumes are usually small, only in some high-power models this parameter exceeds 2 liters. At the same time, manufacturers take into account fuel consumption and select tanks in such a way that breaks do not have to be taken too often.
Max. length
The maximum length of the drill (auger) or drill with which the tool is able to work normally; in fact, this is the maximum drilling depth available when using this model. Note that some models allow, if necessary, the use of longer drills, due to some tricks (you can read more about them in special sources); however, this possibility is far from being available everywhere, and when choosing, it is worth proceeding precisely from the length claimed by the manufacturer.