Comparison DeWALT DCG407N vs DeWALT DCG409NT

Soft start ensures a smooth motor acceleration of the grinder with relatively low acceleration. This is achieved by limiting the start-up current. Soft start performs two functions: it prevents sudden jerks of the tool, reducing the risk of dropping it, and also decreases the load on the electrical network, helping to avoid significant voltage spikes.

The ability to lock the power button prevents accidental presses. Accidental Activation Protection allows safely transporting the switched-off tool from place to place during work breaks without fear of unintentionally turning it on. This feature is also handy when there are small children around. In some models, protection can also be activated when the power is cut off (for example, network failures) — thanks to this, when the power is restored (which can occur at the most unexpected moment), the tool will not start operating without a user command.

A safety system that turns off the tool when there is a critical increase in load. The specific operation method of the electronic motor protection can vary. For example, in some models, it shuts off the motor when there is a sharp increase in load on the working attachment, such as when the disk jams in the material; this helps avoid sharp jerks of the tool, breakage, disk destruction, and other unpleasant consequences. In other models, the protection responds to overheating or a critical excess of current strength. There are also tools that combine both options.

A special brake that stops the engine shaft from rotating after the power is turned off. Thanks to this device, there's no need to wait for the grinder attachment to stop spinning by inertia after finishing work — the rotation stops in just a couple of seconds (whereas without a brake, it could take several tens of seconds). The engine brake not only enhances work safety but also positively affects the tool's lifespan.

Kickback protection is a set of solutions that reduces tool jerking and twisting when the disc binds in material (concrete, metal, stone). It is implemented in two ways: mechanical safety clutch and electronic systems. The clutch (for example, S-automatic from Metabo, SJS/SJS II from Makita) disengages the drive when the torque increases sharply, saving the gearbox and wrist—the tool does not "shoot" out of hands and does not tear gear teeth. Electronics (Bosch KickBack Control, DeWalt E-CLUTCH, Hilti ATC, HiKOKI/Hitachi RFC, Milwaukee AUTOSTOP, Makita AFT) monitors current and accelerations, instantly shutting off the motor and often, in conjunction with a brake, quickly stopping the disc. In comparison: the clutch works even without power, providing a smooth "slip," but the disc continues to rotate briefly; electronic protection shuts down the motor "to zero," but requires functioning electronics and sometimes a restart. In practice, this is important during grooving and cutting of reinforcement, when the risk of binding increases: with protection, the operator controls the tool, reduces dangerous jerks, and protects the gearbox—whether it is a compact 125-mm cordless grinder or a powerful 230-mm corded model.

— Additional Handle. A separate handle for the second hand. In theory, such equipment may make the tool more comfortable to hold with both hands. However, in practice, the absence of an additional handle is often not critical: many tools without it are either designed for one-handed use (like some straight grinders, see "Type") or have other attachments for the second hand (such as a protrusion on the body). So, to answer whether you need an additional handle, you should consider the type and size of the grinder, as well as the specifics of the intended projects. Note also that by default, such a handle is designed for right-handed use, and the possibility of using it in left-handed operation needs to be clarified separately.

— 3-Position Additional Handle. An additional handle installed on a detachable mount and having three installation options: on the left (traditional option for right-handed use), on the right (for left-handed use), and on top (for specific cases — situations when you need to periodically change grip, work in hard-to-reach places, etc.). This function provides extended possibilities for tool customization according to personal preferences. It is mainly found in angular models (see "Type").

— Charger (C). A device for charging the battery in a grinder with the appropriate power type (see "Power Source"). This section usually specifies...the specific model of the charger. Having a "charger" included relieves you from the need to search and purchase it separately; moreover, such a charger is optimally suited at least to the "native" battery, and often to other compatible batteries. The details on the model will be useful primarily in case the included charger is lost or fails, and you have to buy the same or a similar one instead. Moreover, knowing the model of the charger allows you to find detailed data about it and assess the characteristics and features (compatibility with various batteries, additional functions, etc.). At the same time, the configuration "without charger" is also quite popular — see below.

— Without Charger. This feature is indicated exclusively for battery models (machines with other power types — see "Power Source" — by definition do not have a charger, so this point does not need to be clarified for them). The meaning of such a configuration is that modern grinders most often use standard batteries, which also fit other power tools of the same brand and are thus designed for standard "chargers." Thus, if there is already a battery tool "in the household" — the charger for it may turn out to be suitable for the grinder, and you will not need to pay extra for a second copy of the charger. And even if there is no charger available — it can usually be purchased separately without much difficulty (and some tools even allow you to choose the most suitable model of such a device from several options).

— Case / Bag included. The presence of a case or bag for storing and transporting the tool in the supply kit. The case is a suitcase made of durable material and usually has space not only for the grinder itself but also for working tips and other additional accessories. The bag is soft, allowing it to be compactly folded when not needed. Check the availability of a case or bag directly before purchase.

— Dust Collector. A container for collecting dust and other contaminants generated during work. See "Additional — Dust Collector Connection" for more details.

— Extension Pole. A long pole significantly expands the "radius of operation" of the tool: with such equipment, you can reach greater heights, process a large area without moving the platform or other stand, etc. Such capabilities are mainly relevant when processing walls, so the vast majority of grinders with extension poles included pertain to wall sanders (see "Type").

Battery models that the device of the corresponding type is compatible with (see "Power source"). This information will be useful in cases where the battery(ies) must be purchased separately, for example, if the tool does not come with a battery at all, if you need to supplement the original package, or if the existing battery has failed.

Approximate noise level generated by the grinder during operation. Note that this indicator is quite approximate, because. actual "loudness" can vary markedly depending on the type and shape of the material being processed, the surface it is placed on, and other circumstances. In addition, different manufacturers may use different measurement methods. Nevertheless, this indicator makes it possible to assess how comfortable this or that model is in operation and whether special hearing protection is required.

The most “quiet” modern grinders give out about 65 dB — this is comparable to loud speech at a distance of 1 m; in the loudest, the noise level reaches 107 dB — this is the volume of an industrial workshop.

The total weight of the grinder; for battery models (see "Power Source"), usually, it is indicated without taking into account the battery.

This indicator has two meanings. On the one hand, light weight has a positive effect on manoeuvrability and reduces fatigue during work — especially when processing vertical surfaces and ceilings, as well as in other situations where the tool has to be held on weight. On the other hand, for grinders with a vibrational principle of operation (see "Type"), used for processing horizontal surfaces, a significant weight is considered optimal: it allows the tool to fit closer to the material being processed, and also contributes to stability and retention. So when choosing such a model by weight, it is worth considering the features of its intended application.