Types of cordless drills

Reviewers emphasize that for portable power tools, less can be more. If you mainly need to hang pictures and shelves, assemble furniture and other light tasks, experts recommend a small, lightweight cordless screwdriver or pocket driver. At the other extreme, for serious construction projects like a deck or shed, experts recommend a cordless impact driver because it makes driving lots of screws so much easier. Here's a rundown of the various types and uses of cordless drills:

  • Cordless drill/drivers are best for most homeowners. The most common type of cordless tool, these come with bit for both drilling holes and driving or removing screws. An adjustable clutch regulates the torque, or twisting power, applied to a screw. These are best for most homeowners who need both drill and screwdriver functions.
  • Cordless hammer drill/drivers are best for drilling in concrete or brick. These are more powerful but also heavier. They have a specially designed clutch that allows the drill bit to punch in and out while it's spinning. You can disable the hammer action for general use.
  • Cordless impact drivers are best for driving lots of screws. Impact drivers are different from hammer drills. When an impact driver senses resistance, torque increases so the bit is less likely to slip out of the screw head than it would with a regular drill. While capable of drilling holes (usually rather slowly), impact drivers are mainly used for projects that require driving a large number of screws, such as building decks or assembling cabinets or furniture.
  • Cordless screwdrivers. These tools use hex-shank bits so they're usually lighter and more compact than other types -- less tiring to use, and great for working in tight spaces. Subcompact "pocket drivers" use 10.8- to 12-volt batteries, but screwdrivers with lower voltages are fine for hanging shelves or assembling pre-fab furniture. See our separate report on cordless screwdrivers.

If you're just drilling a lot of holes, a cordless drill is best, but if you're drilling a pilot hole, then switching bits to drive a screw, a cordless impact driver is faster and better, partly because it eliminates the need for a pilot hole, partly because it provides about three times as much twisting power. Kits usually include both an impact driver and drill that use the same batteries and charger. You can also buy combo kits that include additional tools.


What size cordless drill or driver do you need?

Cordless drills come in two basic sizes: half-inch and 3/8-inch -- referring to the maximum size drill shank the chuck can accept. For homeowner use, a 3/8-inch chuck still accepts drill bits that make holes much bigger than 3/8 inch. Impact drivers may come with a hex chuck. Hex chucks require special drill bits, but the configuration can make it faster to switch between drilling and driving.

Big construction jobs generally call for the extra power of an 18-volt cordless drill (with a compact Li-ion battery) plus an impact driver. If you have access to a power outlet, experts recommend opting for a corded circular saw for cutting the lumber.

10.8-volt to 12-volt cordless drill/drivers and impact drivers are recommended for basic homeowner tasks. The best of these small, lightweight tools can drive three-inch deck screws, yet are much more comfortable to use than heavier models.

Be advised that many tools labeled 12-volt in 2009 are actually peak 12-volt -- comparable to earlier 10.8-volt tools. For example, Bosch 12-volt tools use the same battery as the earlier Bosch 10.8-volt tools. Since some manufacturers used the higher peak voltage, others such as Bosch and Hitachi followed suit in order to compete.

Price differences among cordless drills of the same voltage, from the same brand, are usually explained by another battery factor: amp-hours (Ah). This is a measure of runtime, or how long the battery will supply power before needing a recharge. Construction crews often opt for higher amp-hours (3.0 or even 3.5 Ah) in order to avoid downtime during the workday. For homeowners, a compact 1.5-Ah battery is usually sufficient, especially if recharging takes 30 minutes or less.


Important cordless drill features

Most cordless drill/drivers now feature variable speed, at least 15 clutch settings for driving screws, at least two speed ranges, forward and reverse settings, and (except for the least expensive models) electric brakes to slow the clutch as needed. An auxiliary handle can greatly improve balance and handling on larger models.

Reviewers say the following additional considerations are most important when selecting a cordless drill/driver:

  • Try tools in person if possible. Comfort is very important. Be sure that you can easily use all the controls and remove and replace the battery. Make sure the tool feels balanced, not front-heavy; experts say this is an important safety consideration.
  • Keep kits in mind when picking a voltage. You can save money by buying a cordless tool kit that shares the same batteries and charger, but remember that some tools need higher voltage than others. For instance, you'll want at least an 18-volt battery to get satisfactory performance from a cordless circular saw or reciprocating saw.
  • Lithium-ion (Li-ion) batteries are usually best. Nickel-cadmium (Ni-Cd) or nickel-metal hydride (NiMH) batteries are budget choices, but Li-ion batteries reduce a tool's weight, last longer and hold their charge a long time between uses. Tests show that some brands don't handle sub-freezing weather well, so if this is a factor be sure to check reviews. Ni-Cd batteries usually handle cold well but are the least environmentally friendly, requiring special disposal because of their cadmium content.
  • Look for a fuel gauge on Li-ion batteries. This type of battery keeps the tool running at full power till recharging is needed, but that means you need some warning for when that time approaches.
  • Look for a smart charger. Many cordless tools come with 30-minute or even 15-minute chargers, which means that a set of two batteries can keep you working as long as you want. Slow charging is one of users' main complaints about cheap cordless drills, especially since some require the battery to cool down before you even place it in the charger. A smart charger lets you know how charging is progressing, and then turns itself off to prevent overcharging.
  • Torque (in inch-pounds) is the basic measure of the amount of twisting force the drill or driver applies. Usually, the higher the voltage, the higher the torque. However, different models with the same voltage do vary. Reviewers say that objective tests are much more accurate than manufacturers' claims.
  • Look for a single-sleeve chuck. This means a bit can be tightened or loosened with one hand. Most drills have this feature or accept hex-shank bits that just click into place. Some reviewers prefer an all-metal chuck, but some soft trim can protect surfaces from damage if your drill or driver slips.
  • Speed ranges add finesse to impact drivers. These tools can have so much torque that it's easy to strip screw heads. Speed ranges and well-reviewed triggers help drive fasteners at the right speed.
  • A pressure-sensitive trigger adjusts the speed within the selected range, so the harder you squeeze the trigger, the faster the chuck spins. This is important so you can decrease the speed as the screwhead reaches the wood, to avoid stripping it or even breaking it off. A sensitive trigger is even more important on an impact driver, since most don't have a clutch to help manage torque.
  • Single-sleeve keyless chucks can be tightened with one hand. Reviewers say they're usually easier to get really tight, while double-sleeve chucks require two hands to tighten. Carbide jaws are a plus, but the most important thing is that the chuck must grip the bits tightly, with no slippage. Some newer drills have chucks designed to keep tightening themselves as they spin.
  • Built-in LED lights are convenient. This feature helps a lot when drilling in a closet or cabinet. Some LEDs are designed better than others, according to reviewers.
  • Built-in levels and bit-storage are nice frills. The level helps you drill accurately, and bit storage (usually a magnetic tray) can speed your work.

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