Comparison DeWALT DCF923N vs DeWALT DCF921N

The size of the mount type "square", provided in the design of the tool.

For the mount itself, see "Chuck type", here we just recall that squares are mainly used in wrenches for installing socket heads. At the same time, for larger nozzles, usually, larger mounts are also used. And the sizes of squares are traditionally indicated by fractional parts of an inch. The most popular option is the 1/2" square, it is the most versatile. Both larger sizes ( 3/4" square and 1" square) and smaller ones ( 3/8" square and 1/4" square) are somewhat less common. ).

Note that there are adapters that allow you to install nozzles of a “non-native” size on a square. However, the possibility of using larger nozzles than regular ones should be clarified separately: the tool may not have enough power for this. In addition, single wrench models are available that initially provide a replacement square and are equipped with interchangeable fasteners — usually 1/4" and 3/8", but other options are also possible.

— Impact Mode. The ability to work in the so-called impact mode. Usually, this mode is switched on and off at the user's discretion, and its meaning and features can vary depending on the type of tool (see "Device"). For example, in drills, impacts are made along the drill axis, typically at a rate of several thousand per minute, positively affecting performance and allowing more efficient handling of hard, dense materials (although such a drill still cannot fully replace a rotary hammer). Conversely, in screwdrivers and impact wrenches, the impact mode would more accurately be called impulse: in this work format, the tool's attachment rotates in separate jerks, usually at a frequency of about 3,000 per minute. This also enhances work efficiency, which is especially useful when screwing screws into dense material and loosening old, "stuck" fasteners.

— Power Button Lock. A function that allows the power button to be fixed in the pressed position. Usually, it has the form of an additional button installed either on the main trigger or nearby. This function is very convenient in situations where the tool has to be used for a long time without breaks — for instance, when drilling several dozen holes: it is easier to fix the start button in the on position than to hold it down constantly, further straining the finger on the working hand. And the lock is usually turned off in the simplest way — for exampl...e, by briefly pressing the same start button.

— Speed Control. The ability to additionally limit the tool's speed. Smooth adjustment is present in almost all modern models: the harder the start button is pressed, the higher the speed. This allows you to adjust the tool's operation mode on the fly to suit the situation's characteristics. And this regulator allows setting the maximum rotation speed, so even when the button is pressed "to the limit," the working nozzles' speed does not exceed the set value. This function is indispensable for some tasks requiring precision — notably when handling delicate materials where too high a speed is fraught with damage.
It is important to note that having a speed controller is not related to the number of speed settings (see above). For example, a tool may very well have several speed modes, each of which can have its speed further limited by the controller.

— Speed Maintenance. A function that allows maintaining a constant rotation speed of the nozzle, regardless of the load on it. Without special regulation, at the engine's constant power, the rotation speed inevitably decreases with increased load and increases with decreased load. And the speed maintenance system monitors resistance on the nozzle and, if necessary, changes power so that the rotation speed remains constant. This positively affects both the quality of work and the longevity of the nozzles and the entire tool.

— Brushless Motor. The presence of a brushless (commutatorless) motor in the power tool. Such motors significantly surpass traditional commutator motors in efficiency, which allows for a noticeable reduction in energy consumption without sacrificing power; this is especially important for battery-powered tools (see "Power Source"), where this feature is predominantly found. Besides, brushless motors are less noisy and practically do not produce sparks during operation, making them ideal for work in increased fire hazard conditions. Their main drawbacks are traditional — complex design and high cost.

— Lighting. Built-in light for illuminating the work area. This function can be useful both in evening/night time and in hard-to-reach places where outside lighting poorly penetrates, and also in situations where this lighting is too dim. In most cases, it is implemented with a single LED that lights the working area in front of the tool.

— Ring Lighting. An advanced lighting system where LEDs are arranged around the chuck, allowing for even illumination of the drilling or screwing area. Thus, light falls not from the side but precisely around the working part, reducing interference from shadows cast by the body, hand, or bit. This helps start drilling more accurately, hit the slot with the bit more neatly, and work more confidently with small fasteners. In practice, ring lighting is especially convenient when assembling furniture, installing shelves, working under a sink, or repairing places where little general light penetrates.

— Display. Own display on which various information about the work and state of the device can be displayed — for example, the torque set in the settings or the rotation speed, and in battery models — also a battery charge indicator. Such a screen provides additional convenience and visibility; however, overall, it is quite a specific function that is extremely rare in modern power tools — for instance, speed or torque indicators can be provided directly on the regulator, while a simple LED that signals by blinking or changing color can be used as a charge indicator.

— Smartphone Synchronization. The ability to connect the tool to a smartphone or other gadget (for example, a tablet) via Wi-Fi or Bluetooth. Such a connection is usually used to adjust work parameters like speed or torque; doing this through a mobile app is often more convenient than through the controls on the tool itself. And some models with this feature allow you to set access via a password: the tool simply will not respond to the start button until the correct password is entered on the controlling gadget.

— Built-in Bubble Level. An integrated device for controlling the angle of the tool relative to the horizon. As with regular levels, the scale's role in such devices is played by a sealed vial with marked lines containing brightly colored liquid and an air bubble. By the position of this bubble relative to the marks, the entire tool's position is determined — namely, its alignment with vertical, horizontal, or a predetermined tilt angle (the latter option is virtually never found in built-in levels). In manual tools, usually a single-axis level is provided, reacting only to deviations from horizontal forward or backward, while models with the ability to be mounted on a stand (see below) may also have a circular level, checking vertical alignment and detecting deviations from it in any direction.

— Bit Compartment. A storage place for interchangeable attachments directly in the tool's housing, handle, or battery base. Most often, it is a simple slot or holder for one bit, so the most frequently used attachment is always at hand and does not get lost during work. Less commonly, there is a drum compartment or built-in magazine for several bits.

— Water Cooling (SOL). The presence of SOL in the tool — a liquid cooling system (most often plain water) supplied to the working nozzle using a built-in pump. Such a system performs several functions simultaneously. Firstly, it actually cools the nozzle, preventing damage due to overheating. Secondly, the liquid slightly reduces friction at the contact point, further reducing load on the nozzle and increasing its durability. Thirdly, water absorbs the dust formed during drilling, preventing it from dispersing into the air and entering the lungs of surrounding people; and cleaning after work is significantly simplified. On the other hand, water cooling systems are quite expensive and bulky, and for relatively simple tasks and low loads, it is quite possible to do without SOL.