Cordless drills run on battery power. Because of their demands, drills require lithium-ion batteries. These batteries are rechargeable and offer significantly more power than traditional batteries. They can power drills with motors that require 450 watts and more. Most drills use 18-volts, though smaller ones use only 12 volts. The benefit of lithium-ion is that they hold a charge for a long time and recharge quickly. Lithium can have 3-5x more battery life, endure more charges, and recharge in as little as 15-30 minutes. Many drill brands produce their own batteries and include the required number (usually 2) in the box as well as the battery charger.
The speed on a cordless drill is measured in RPMs, or, revolutions per minute. This can be confusing, since materials (wood, iron, etc) often use a different measure for speed, called SFM. This represents the speed necessary for a cutter to be pushed in a straight line. To figure out the SFM using the RPMs, the formula is (.26) x RPM x diameter. As a general rule, you want to use a slower RPM for very hard materials like steel, and a faster one for wood. For more versatility and precision, the RPMs on drills bits are variable, so you can easily choose a slower RPM if necessary from a drill that includes high RPMs. Drills usually get at least a two-speed gearbox, so you can set the speed from 0-400, or 0-1,300, give or take. Especially fast drills can even have variable speeds of 0-500 and 0-1,700, or even a 3-speed, all-metal transmission.
In addition RPMs, drill power is measured in torque. Really difficult woodworking and masonry jobs require a lot of torque, which is the term for how much force is needed to twist an object, in a drill’s case, a screw. If you own a piece of equipment like a rototiller, you are familiar with how torque plays out in the real world and how important it is when working through solid ground. It is essentially the same with drills, except it’s measured in inches and not feet, and the materials you’re working through are wood, concrete, and so on as opposed to dirt. Smaller, less powerful drills intended for jobs like hanging pictures and lighter woodworking can have as little as 100 inch/pounds, while heavy-duty drills boast 450+ in/lb.
Clutches are not present on corded drills, so you may not know how to use the clutch on your cordless model. Clutch settings allow you to choose the right angle and depth for the material you’re working on, so you don’t damage it. This would be important if you’re working with drywall, which is prone to tearing. A lot of clutch settings let you work on a variety of materials and makes your drill more versatile. In terms of how positions you get, drills start with 10 and can have as many as 20+.
Chuck clamps are the part of the drill where you insert the bit or other rotary tool. Many chucks have star-like jaws (also called “dogs”) that grip the bit. Most drills have three dogs. You can tighten or loosen the jaws with a wrench-like tool called a chuck key. Many chucks are now keyless, which means you can tighten/loosen them by hand. Some even tighten as you work, which ensures a powerful grip and more secure drilling. Keyless chucks make changing out bits easier and faster than with a keyed chuck. Most chucks on cordless drills are either ½-inch or ⅜ inch, which fit a variety of bits for different jobs.
Drills are built from hard plastic and metal, so they stay safe against debris and accidental drops. Rubber bumpers also protect a cordless drill against wear and provide soft, ergonomic grip for the user. Steel-enforced collars serve as an additional guard against wear from temperature changes, harsh weather and so on, while protections on the motor can shield the tool against overheating or stalling.
Cordless drills are automatically more convenient than their corded counterparts, but there are other features to be on the lookout for. Weight is a concern, since you do not want your arm to get tired after using the drill for a long time. Cordless drills can be as light as 3-3 ½ pounds and reach 5 or so pounds if they’re larger. Most drills are also pretty compact, so you can use them in more cramped spaces. For working in darker environments, most drills now include a built-in LED light.