How to Choose a Cordless Drill Driver

In the DIY and tools department, power tools are the largest purchase and the one where the specification sheet is easiest to misread. A cordless drill driver drills holes and drives screws, and its performance depends as much on the battery as on the tool. This guide explains the figures on the label, how battery voltage and capacity work together, and how to match a drill to the jobs you actually do.

Voltage: 12 V, 18 V and 20 V

Voltage indicates the power class. 12 V tools are compact and light, suited to assembling furniture, hanging shelves and light drilling in wood. 18 V tools are the standard for general home and workshop use, with enough power to drill into masonry with a hammer function, to bore large holes in wood and to drive long screws.

You will also see 20 V labels. Many 18 V and 20 V batteries are the same hardware: the 20 V figure is the maximum voltage when the battery is fully charged and not under load, while 18 V is the nominal figure under load. Both labels often refer to five lithium-ion cells in series. Do not assume a 20 V tool is more powerful than an 18 V one; compare torque and the actual specification.

Battery platforms matter. Batteries are generally not interchangeable between brands, and often not between a brand's different ranges. Choosing a platform that also includes the other tools you may want, such as an impact driver, jigsaw or sander, lets you share batteries and chargers.

Battery capacity in Ah and Wh

Ampere-hours (Ah) describe how long the battery runs. A 2.0 Ah battery suits occasional use, 4.0 Ah is a common step for regular tasks, and 5.0 Ah and above is for heavy, long sessions. A higher capacity means more run time but also more weight, and a bigger battery can make a drill feel front or rear heavy.

To compare across voltages, multiply: 18 V x 4.0 Ah is about 72 Wh. Capacity does not increase the power. A big battery does not make a drill faster, only longer-lasting. Higher-draw tools, such as hammer drills used in concrete, heat batteries faster and drain them quickly regardless of capacity.

Check the charger. A standard charger may take 60 to 120 minutes for a mid-sized pack, a fast charger less. Lithium-ion packs dislike heat and deep discharge, so store them partly charged in a dry room and do not leave them in a hot car.

Torque, speed and clutch

Torque is the turning force, in newton metres (Nm). Entry-level drills offer 30 to 40 Nm, mid-range 50 to 60 Nm, and strong models 80 Nm and more. Note that the figure given is often maximum, not what is available on every setting. Higher torque helps with large screws and wide holes, but a lighter drill with moderate torque is easier to handle for general jobs.

Most drills have two gears. Low gear provides more torque and slower speed for driving screws and large holes. High gear provides faster rotation, roughly 1,500 to 2,000 rpm, for smaller drill bits. The clutch is the numbered collar that stops the drill when it reaches a set torque, so screws are not driven too far. A range of 15 to 20 positions is common.

Brushless motor, chuck and hammer function

Brushless motors have no carbon brushes to wear out. They are more efficient, run cooler and extend the battery run time, but the tools cost more. For occasional DIY, a brushed motor is adequate; for frequent use, a brushless motor is justified.

The chuck holds the bit. A 10 mm chuck suits most domestic work, while 13 mm fits larger bits. Keyless chucks are standard, and a single-sleeve chuck can be tightened with one hand. A hammer drill function adds a pulsing action for brick and concrete. It is only useful with masonry bits. Without it, a drill is not appropriate for concrete walls.

A word on drill presses

A drill press is a stationary machine fixed to a bench, which makes holes straight and consistent. It is sold in the same department and suits workshops where you drill many holes of the same depth. Check the chuck capacity (often 13 or 16 mm), the motor power in watts, the number of speed steps, the depth stop and the table size. Use clamps or a vice for the workpiece, and wear eye protection. A press complements a cordless drill rather than replacing it.

Safety and ergonomics

Hold the drill and check the weight with a battery fitted. Look for an LED work light and a belt clip. A kit that includes a hard case, two batteries and a charger is often more practical than a bare tool. Wear eye protection when drilling, and use ear protection with a hammer function. Keep clothes and hair away from the chuck.

Pre-purchase checklist

• Which jobs are planned: furniture, wood, metal or masonry?
• Is 12 V enough, or is 18 V and 20 V needed?
• Does the kit include a battery of adequate Ah capacity, and a spare?
• Is the torque, clutch range and two-speed gearbox suitable?
• Is a brushless motor worthwhile for the amount of use?
• Does the chuck size match your drill bits?
• Do you want to continue with the same battery platform for other tools?