Screwdrivers, also known as turn screws, are hand-held, manually-powered implements designed for the insertion and tightening of screws. They are made up of a head or tip, which engages with a screw; a mechanism to apply torque by rotating the tip; and a way to position and support the screwdriver.
The popular tool has a handle and a shaft that enable it to be positioned and supported, and when rotated, to apply torque. A screw has a head with a contour for appropriate screwdrivers tips to engage it in such a way that the application of sufficient torque to the screwdriver will cause the screw to rotate with the force of one hand.
Screwdrivers come in a large variety of sizes to match those of screws, including tiny tip options for jewelers, cabinet makers, gunsmiths. Common tips include Phillips, slotted (flat-head or 'standard'), six-point, square tip, or stubby.
If a screwdriver is not the right size and type for the screw used, it is likely that the screw will be damaged in the process of tightening it. When tightening a screw with force, it is important to press the head hard into the screw, to avoid damaging it. Some tips of screwdrivers are magnetic, allowing the screw to remains attached to the screwdriver without requiring external force. This is particularly useful in small screws, which are otherwise difficult to handle.
Screwdrivers may have the option of coming with interchangeable heads, being power driven, having soft handles, being made of a hardened-alloy construction, and being ratcheted or magnetized screwdrivers. The handle and shaft of the tool have changed considerably over time; the design is influenced by both purpose and manufacturing requirements.
Screwdrivers are widely used for machine screws, wood screws, mechanical assemblies, building and construction, bolt assemblies, and fastener assemblies. They are often used in the home and construction settings.
The increase in popularity of this tool ultimately leads to the refinement and eventual diversification of screwdrivers. Refinement of the precision of screws has also considerably contributed to the boom in production, mostly by increasing its efficiency and standardizing sizes. Screwdrivers remain one of the most common tools both in household use and in professional manufacture.