Screwdriver

A screwdriver is a hand tool designed to turn screws by applying torque to their heads. It usually consists of a handle and a metal shaft ending in a shaped tip that fits into a particular type of screw head. Common tips include the flat-blade type, used with slotted screws, and the cross-shaped Phillips type. Other designs, such as Torx and hexagonal tips, are made for screws with matching recesses.

When the handle is turned, the shaft transmits the applied torque to the tip, which pushes against the surfaces inside the screw head and makes the screw rotate. The fit between the tip and the recess is important because a poorly matched tool can slip and damage the screw. Screwdrivers come in different sizes and shapes because screws vary in diameter, head design, and required torque.

Some models have insulated handles for electrical work, while others have interchangeable bits that allow one handle to work with several screw types. A manual screwdriver relies entirely on the user's hand to produce the turning force, whereas an electric or cordless screwdriver uses a motor to rotate the bit.

To tighten a screw, the tool is normally turned in the direction that drives the screw into the material; to loosen it, the direction is reversed, although the exact convention depends on the screw. Applying steady pressure along the screw's axis helps keep the tip engaged and reduces slipping. Choosing the correct tip and size makes the work easier and helps prevent damage to both the tool and the screw.