How Power Drills Work

Power Drill Parts

The power drill is remarkably easy to use, so it makes sense that it's a remarkably simple machine. Basically, a squeeze of the trigger turns on the electric motor, which then rotates the drill or screwdriver bit. However, advancements in drill design and control mean there's a little more to it than that.

The first thing you need to know about power drills is how they're powered. Current models are both corded and cordless; corded drills are rated in amps, while cordless drills are measured in volts. The higher the amperage or voltage a drill has, the more power it has. More power creates more torque, or rotational force, on the drill or screwdriver bit.

A trigger switch, located in the same place you might expect the trigger of a pistol, gets the drill moving. Today's drills usually have a variable speed trigger, meaning that the harder you squeeze, the faster the electric motor spins the drive shaft. Cheaper models run at a single top speed, but pricier models offer between two and four maximum speed settings, usually ranging between 200 and 2,000 rpm. With a variable speed trigger and multiple speed settings, you can operate your drill between zero rpm and the top speed of each setting.

From the electric motor, the drive shaft transmits the rotation through the clutch, which regulates the drill's torque. Many drills have an adjustable clutch, some with as many as 24 settings. The higher the clutch setting, the higher the torque a drill puts out. When the drill reaches the preset clutch setting, the clutch disengages the drive shaft, allowing the motor to turn but not the drill or screwdriver bit. This results in a clicking sound.

The last major part of a drill is the chuck, a mechanism into which you fasten the drill or screwdriver bit. Until the 1980s, chucks were keyed, meaning you needed a special tool to tighten them. Today, nearly all drills are keyless. The gear once tightened by a key is fitted with a grip, allowing the user to secure the bit by hand.

Read on to learn about selecting the right drill or screwdriver bit for the job, and discover ways in which you might not have thought to use power drills.