Comparison Bosch GBH 2-28 Professional 0611267500 vs Metabo UHE 2250 Multi 690540000

The power given out by the perforator directly to the drill or other working equipment. This figure is inevitably lower than the power consumption (see below) due to energy losses in the tool mechanisms.

In general, higher net power means more efficiency and productivity; the reverse side of these advantages is an increase in price, energy consumption, dimensions and weight (however, the latter is not always a drawback for rotary hammers). In addition, note that tools with similar useful power values may differ in the ratio of chiseling speed and impact power: remember, a higher frequency means less energy for each individual impact, and vice versa. So the big numbers in this paragraph can mean both high efficiency when working with hard, stubborn materials, and good performance on relatively simple tasks; these features need to be specified separately.

Also, by the ratio of useful and consumed power, one can evaluate the efficiency of the tool in terms of energy consumption: the lower the power consumption (with the same useful power), the more efficient this model is. The downside of energy efficiency is often increased cost, but it can be recouped fairly quickly in energy savings, especially if you work long hours and often.

Rated power consumed by the rotary hammer during operation. Usually, the maximum power consumption in normal operation is taken as the nominal power.

In general, the higher this indicator, the heavier and more performant the rotary hammer is, the more advanced its performance usually turns out to be. On the other hand, the electricity consumption of such tools is high. In addition, note that with the same power consumption, the actual set of individual characteristics for different tools may be different. For example, frequency and impact energy are inversely related, and for the same power input, higher frequency usually means less individual impact energy. So, according to this parameter, it is worth evaluating only the overall level of the instrument; for accurate selection for specific tasks, you need to pay attention to more specific characteristics.

Also note that power consumption data can be useful for some tasks related to catering — for example, if a construction site is powered by an autonomous generator and you need to estimate the load on this energy source.

The energy transmitted by the perforator to the material being processed upon impact; the higher this indicator, the stronger and more powerful each individual blow.

First of all, we recall that the energy of impacts is directly related to their frequency: an increase in frequency leads to a decrease in energy. Therefore, for models where the number of strokes can be adjusted, this paragraph usually gives the maximum energy achieved at the minimum speed of operation.

In general, higher impact energy improves efficiency when working with hard, stubborn materials, but requires more motor power (especially if it has to be combined with a high frequency). Therefore, it is worth choosing according to this parameter, taking into account specific tasks. So, for occasional use in everyday life, an energy of 2 J or less is enough, for home repair work of medium intensity, at least 3 J is desirable; a power of 4 J or more is already considered high; and in some industrial-grade perforators, this figure can reach 30 J.

The number of beats per minute provided by the punch. For models in which the beat frequency can be adjusted, this item indicates the entire adjustment range, for example "1600 — 3000".

High impact frequency, on the one hand, increases the productivity of the tool and can significantly reduce the time required for work. On the other hand, with the same engine power, an increase in the number of strokes per minute leads to a decrease in the energy of each stroke. Therefore, among heavy performant devices, a low frequency is often found — up to 2500 beats / min and even lower. And the ability to adjust the frequency of impacts allows you to adjust the hammer to the specific situation, depending on what is more important — productivity or the ability to cope with hard, stubborn material. For example, for old crumbling brickwork, you can set the speed higher, and for working with stone or dense concrete, it is better to reduce the frequency of impacts by directing engine power to increase the energy of each impact.

Summing up, we can say this: when choosing a perforator, you should focus on both the number of strokes and the impact energy. Detailed recommendations on this subject for specific situations can be found in special sources.

The speed of rotation of the working equipment provided by the rotary hammer. Usually, this indicates the speed at idle, without load; rated load speeds can be further specified in the characteristics (see below), but this is rare, and this parameter is still considered the main characteristic. It is also worth mentioning that in the presence of a speed controller (see "Functions"), the maximum speed value is given here.

When working in the main mode — drilling with impact — the rotation of the equipment is used mainly to remove waste from the hole, and the revolutions here are of no fundamental importance (they can be very low). Therefore, it is worth paying attention to this indicator mainly in cases where the rotary hammer is planned to be often used for conventional drilling, without impact. And here it is worth proceeding from the fact that high speeds increase productivity and contribute to accuracy when working with some materials, but reduce torque (compared to tools with the same engine power). So for heavy work with hard, stubborn materials, relatively "slow" tools are usually better suited.

Note also that drilling is not the main task of rotary hammers; therefore, their rotation speeds are noticeably lower than those of the same drills. On the other hand, in this case, low speeds are often compensated by powerful engines and high torque, which makes it possible to effectively drill holes...of a fairly large diameter, including using crowns.

The revolutions developed by the rotary hammer motor at the rated load on the tool.

Rated is usually considered the greatest load that the tool is able to transfer without breakage for a sufficiently long operation. Anyway, this parameter is indicated relatively rarely, since idle speed is traditionally considered the main characteristic (see "Number of revolutions" above). However, load speed data also allows you to evaluate some of the features of the rock drill. So, higher rated load speeds (at the same idle speed) in fact means at least higher productivity, and in many cases also the ability to cope with complex tasks more efficiently.

The maximum torque developed by the rotary hammer.

Without going into too much detail, torque can be described as the working force of a tool. For drilling with impact, this indicator is not of fundamental importance — we recall that the rotation of the nozzle in this mode performs an auxiliary function, and the key parameters are the frequency and energy of impacts. But with traditional drilling, without impact, the torque directly determines the effectiveness of the tool. The higher it is, the more powerful the impact on the material being processed, and the larger the drilling diameter this model can provide. However tools with similar drilling diameter limits may differ in torque; in such cases, you should assume that more operating force requires a more powerful motor and affects the cost, but it contributes to reliability and provides additional guarantee in case of some abnormal situations.

The reducer is a mechanism that transmits rotation from the tool engine to the chuck with equipment. This reduces the speed of rotation, but increases the torque.

The simplest modern gearboxes are single-speed, with a constant gear ratio. They are standard equipment for modern rotary hammers, are used in the vast majority of models and have no special features worth mentioning. Therefore, in our catalog, the type of gearbox is specified only if it is a more advanced two-speed gearbox, with two gear ratio options (and, accordingly, two speed modes of rotation of the cartridge). Such mechanisms are more complicated and more expensive than single-speed ones, however, they provide additional features for customizing the punch to the specifics of the situation. So, at low speed, maximum torque is achieved, which allows you to effectively cope with hard materials; and if the material is relatively soft and the resistance is low, you can switch the gearbox to higher speeds, achieving greater performance.

At the same time, it is worth noting that the advantages of two-speed gearboxes are relevant mainly for drilling without impact, which in general is not the main task of rotary hammers. Therefore, there are few tools with this feature.

The type of cartridge used in a rotary hammer to hold a working tool.

— SD+. Abbreviation for it. "Steck-Dreh-Sitzt" — "insert-turn-fixed." Today's most common rotary hammer chuck, used in low and medium power models. It has a 10mm diameter shank with 4 slots and accepts tools from 4 to 26mm in diameter and 110mm to 1000mm in length. The advantages of SDS + are the reliability of fastening and convenience when changing tools — it does not require additional devices such as keys. The main drawback is the significant beating of the tool during rotation, due to which such a cartridge is very poorly suitable for drilling.

— SDS Max. Modification of the SDS + cartridge (see above), intended for use in powerful professional models. It has a shank diameter of 18 mm and allows the use of tools with a diameter of up to 55 mm; otherwise similar to SDS+.

— SDS-Quick. A variation of the SDS cartridge (see above), in the shank under which protrusions are used instead of grooves. It is also possible to install tools with 1/4" hex shanks in such a chuck. The most common tool diameter for SDS-Quick is 4-10 mm. This chuck is used relatively rarely.

— Quick release. Chuck for holding drills and other tools used in drilling holes. The design is similar to those used in electric drills — it has 3 cams, it is designed for a too...l with a cylindrical shank without grooves, and hand force is enough to install / remove the tool. Such a cartridge is devoid of the main drawback of SDS — beats during rotation; this allows you to use the rotary hammer for drilling with good quality. On the other hand, it is much worse for chiselling than SDS. Therefore, keyless chucks are usually supplied as an accessory and are installed instead of the standard SDS chuck.

— Key. The presence of a special key cartridge in the delivery set of the rotary hammer, usually in addition to the standard SDS (see above). In terms of mounting design, this chuck is similar to the keyless chuck (see above) and is also designed for use in drilling. Its main difference lies in the method of installing / removing the tool: you can’t do this with your bare hands, you must use a special key to compress / unclench the cams. Such a system is somewhat more reliable than a quick-clamping system, but much less convenient: changing a tool takes a lot of time, and the key can be lost.