Power drivers are, for practical purposes, redesigned and re-engineered electric drills. Drills and drivers look much like one another, but instead of an adjustable chuck that can grip a wide range of drills, the power driver accepts only standardized screwdriver bits, usually Phillips-head, but slotted and other head types can also be used.
Not everyone needs a power driver. Originally, they were designed for use by installers of dry wall (hence, another name by which they are known, drywall screwdrivers). In the hands of an experienced user, they drive drywall screws at a remarkable rate, saving time and, for a contractor, money.
Like electric drills, a power driver should be reversible and have a variable speed control. Drywall drivers are approximately the size of three-eighths-inch drills, and share their pistol-shaped design equipped with trigger control. Drivers also have a locking button that, when engaged, keeps the drill running continuously.
Power drills look slightly different because they have an adjustable cone that surrounds the tip of the bit. This nosepiece acts as a stop, causing the bit to cease driving the screw at a preset depth. To facilitate feeding screws onto the bit when the driver is running continuously, a positive clutch mechanism at the base of the bit holder acts to engage or disengage the spinning motor. Only when the bit is pushed onto the workpiece does the clutch cause the bit to turn.
A standard electric drill will accept screwdriver bits and, for occasional use, will perform the same jobs quite adequately although it lacks the power driver’s stop and clutch mechanisms. However, if you are planning on hanging a quantity of dry wall, a drywall screwdriver is by no means an unnecessary extravagance. Off-the-shelf electric drills are not designed for the demands of driving screws and if they are used as drivers for extended periods, their life expectancies may be shortened significantly.
There is another class of driving tools on the market that can perform a range of light-duty driving chores. Known as in-line screwdrivers, these rechargeable cordless drivers are light (most models weigh less than two pounds) and handy for removing and driving screws around the house. They do not have the torque for heavy-duty tasks, but are easy to store and use.