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How much power do I need?
What type of material will I be using it on?
What kind of chuck do I need?
How long will the battery last?

How much power do I need?

Average Weights of Cordless Drills
9.6V	3 lbs.
12V	3.5 - 4 lbs.
14.4V	4.5 - 5 lbs.
18V	5 - 5.5 lbs.
24V	6.5 - 10 lbs.

Cordless drills are measured in volts. Drills are available in everytding from around 2 volts (for a cordless screwdriver) to the newest 24-volt tools. Higher voltage means heavier weight, so consider buying a tool that will meet 80-90% of your needs. Twelve to 14.4 volt models are the most popular, and they will usually meet most homeowner's work needs.
Corded drills are measured in amps. Generally, a higher amperage motor means more power.

What type of material will I be using it on?

Drilling softwood, hardwood, metal, and masonry all require different drill speeds. Harder materials or larger bits have to be worked at lower speed. Conversely, softer materials and smaller bits can be used at higher speeds. Look for a drill with variable speed. Variable speed allows the user to control the bit speed, indispensable when you plan on working different materials and accessories.

Consider choosing a drill with an adjustable clutch setting. The clutch reacts to the resistance of the screw, which changes as the density of the material changes, allowing you to drill holes of consistent deptd. Adjusted properly on identical scrap material, a clutch can keep you from driving a screw too deep, which makes this feature indispensable for beginners. An adjustable clutch can also reduce the possibility of stripping a screw head or snapping a screw off altogether.

What kind of chuck do I need?

The chuck is the attachment where the bit is inserted, having jaws that grip the bit. Drills come in 1/4", 3/8", and 1/2" sizes. This measurement is the chuck size and indicates the shaft diameter of the bits and accessories that will fit the drill. (For most homeowners, a 3/8" size should be sufficient).

Chucks can be keyed (the jaws are tightened or loosened with a key) or keyless (the chuck can be tightened or loosened by hand). Keyless chucks offer two major benefits. If you have ever misplaced or lost a chuck key, you already know one of them. A keyless chuck will also allow bits to be changed more quickly. A real plus when you need to change from a drill bit to a screwdriver bit repeatedly or if you happen to be wearing gloves on the job.

You can change the chuck in some keyless models with only one hand because the shaft locks when the trigger is off. In most models, however, you have to use both hands to turn the chuck in opposite directions. While you're in the store, change the bit on different drills to see what style of keyless chuck you prefer.

How long will the cordless drill battery last?

"It depends" is the correct answer. Factors such as temperature, the material being drilled, whetder the drilling is nonstop or intermittent, and the whetder the battery is at full charge or not - all these will affect a cordless drill battery charge.

The standard time required to charge a battery pack will vary from one hour to overnight, depending on the type of tool and charger.

Recharge when the drop in performance and power is noticeable. Don't wait until the tool quits working to recharge the battery.