Cordless Drills: What To Look For

Types of cordless drills

While it's tempting to get the biggest, most powerful cordless drill you can afford, 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.

• Cordless screwdrivers. Sometimes called pocket drivers, these are small, simple and lightweight tools, good for hanging shelves and pictures or assembling furniture.

If you're just drilling a lot of holes, a cordless drill is faster. But if you're drilling a pilot hole, then switching bits to drive a screw, a cordless impact driver is the faster and better tool, partly because it eliminates the need for a pilot hole.

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 less expensive 3/8-inch drill is big enough, unless you're planning a lot of major construction projects. You can still fit drill bits into a 3/8-inch chuck that drill holes much bigger than 3/8 inch. Impact drivers may come with a hex chuck. If you want to drill holes with a hex-chuck tool you'll need special drill bits -- but this configuration can make it faster to switch between drilling and driving.

As for battery voltage, experts recommend 10.8-volt to 12-volt cordless drill/drivers and impact drivers for most homeowner tasks. Reviewers find that 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 10.8-volt tools on the market earlier. For example, the 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.

Note that the price differences among cordless drills of the same voltage, from the same brand, are usually explained by another factor in batteries: amp-hours (Ah). This is a measure of runtime -- how long the battery will power the tool before needing a recharge. Construction crews often opt for higher amp-hours in order to avoid downtime during the workday. For homeowners, a compact battery is usually sufficient -- especially if recharging takes just a few minutes.

Important cordless drill features to consider

Reviews say that most cordless drill/drivers now have 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. Except on subcompact models, an auxiliary handle can greatly improve balance and handling.

Reviewers say the following additional features matter most when selecting a cordless drill/driver:

• Try tools in person if possible. Be sure the tool feels really good to hold, that you can use all the controls and remove and replace the battery with comfort. Make sure the tool feels balanced, not front-heavy; experts say this is an important safety consideration.

• 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. 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.

• Built-in LED lights are convenient. This feature helps a lot when drilling in a closet or cabinet. Reviewers say some LEDs are designed better than others.

• Built-in levels and bit-storage are also nice frills. The level helps in drilling accurately, and bit storage (usually a magnetic tray) can speed your work.

• 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 control 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.