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How Power Drills Work

Choosing a Power Drill
Choosing the right power drill can make a huge difference with your home improvements.
Choosing the right power drill can make a huge difference with your home improvements.

With dozens of models to choose from, deciding which drill to buy can be an overwhelming task. The key is to choose a drill that fits your needs.

One of the first things you need to consider is the drill's power supply. Corded drills never have to be recharged and are often more powerful than their cordless counterparts. But then there's the cord -- it gets in the way and restricts use to jobs near an electrical outlet. Cordless models can be taken almost anywhere but can't run forever. For this reason, it's a good idea to purchase an extra battery so one can charge while the other is in use. Battery voltage ranges from 9.6 to 18; higher voltage commands more torque, but 12- to 15.6-volt models are typically powerful enough for everyday use. High voltage, along with high amp-hour (Ah) ratings, guarantee longer battery life.

But how does the drill actually perform? We've already mentioned a number of features that'll make your home improvement experience more productive and enjoyable. First is the variable speed trigger which allows greater control over the speed of the bit. An adjustable clutch is also important, particularly for driving screws. A drill operating with too much torque has broken many a screw head. It's also important to choose a drill that's right for the tasks for which you plan to use it. One way to determine this is by chuck size, or the size of bit that the chuck can accept. Common sizes are 1/4, 3/8, and 1/2 inch (metric chucks are 6, 8, 10, or 13 mm); the higher the diameter, the higher the torque. For most household tasks, the 3/8 inch (10 mm) chuck diameter provides plenty of torque, but if you plan to drill into more dense materials like metal or concrete, you might consider something a little larger. Finally, you'll have to decide if you want a drill with the impact feature. While this doesn't provide any advantage for drilling holes in wood, it makes screwdriving easier and is necessary for drilling in concrete or masonry.

Another criterion that often gets overlooked is the feel of the drill. When choosing one, pick it up and see how it handles. Is it too heavy? Does it feel balanced in your hand? Is the speed setting easy to adjust with your thumb and index finger?

With these considerations in mind, you'll be ready to get drilling. For lots more information on home improvement, see the links on the next page.