DEWALT DCD799B 20V MAX ATOMIC hammer drill, tool only

Unit Watts Out (UWO) is one maker's own measure of a drill's power output, combining speed and torque. It is useful for comparing that maker's drills against each other. It is not an industry standard and other makers do not publish it, so it cannot be compared directly with torque figures elsewhere.

Max speed is the top no-load speed, in RPM for rotating tools. No-load means the tool is running free, so speed drops once it is working. On drills, many makers list a figure per gear: high for small bits, low for control with large bits or long screws.

Hammer rate, in blows per minute (BPM), is how often the bit pulses forward while drilling in hammer mode. It matters for drilling brick, block and concrete. Hammer drills suit occasional masonry holes; frequent or large holes in concrete usually call for a rotary hammer.

The chuck holds the bit. A keyless chuck, sized by the largest shank it accepts (often 3/8 or 1/2 inch), tightens by hand and takes round or hex shanks. A 1/4-inch hex quick-change collet, used on impact drivers, takes hex-shank bits only and allows fast one-handed bit changes.

Tool length is the front-to-back measurement published by the maker. A shorter tool fits between studs, joists and inside cabinets more easily; standard US framing is 16 inches on center, leaving about 14-1/2 inches between studs. Check whether the figure includes the chuck or bit holder.

Brushless motors use electronic control instead of carbon brushes, which generally means less wear, less heat and more runtime per charge. Brushed motors are simpler and often cheaper, and are fine for lighter or occasional use, though their brushes can wear out over time.

This lists how many batteries come in the box, if any. Tool-only (bare) listings include no battery or charger, which suits buyers already on that battery platform. Two batteries let you charge one while working with the other.

Amp-hours (Ah) is the battery's charge capacity. At the same voltage, a higher Ah pack runs longer between charges but is usually larger and heavier. Smaller packs keep the tool lighter for overhead and light work; larger packs suit saws, grinders and other high-draw tools.

This states whether a charger is included and which type. Chargers vary in output, so the same battery can take noticeably different times to charge on different chargers. Tool-only listings usually include no charger.

The clutch slips at a set torque so screws are not overdriven, stripped or sunk too deep. More settings give finer steps of adjustment, useful for small screws, soft materials and cabinet hardware. A drill mode usually bypasses the clutch for full torque when drilling.

This lists what the tool ships in: a hard case, a soft bag, a stackable storage box, or nothing. Tool-only listings often come with no case. Kit contents can change over time, so check the current listing before buying if the case matters to you.