A screwdriver is a versatile tool, either manual or powered, for driving a screw. As a general practice, screwdrivers are classified by the tip that fits into the driving surfaces which are designed slotted, grooved or recessed. The screwdriver tip fits screws of same size and type for optimum compatibility. You get screwdrivers in a broad variety of types and sizes of tips to engage screw heads with corresponding properties. There are screwdrivers with a handle and shaft, fitted with detachable tips to engage different types of screws with ease.
These removable tips, called bits, are so designed to fit snugly with the shaft of the handle of the screwdriver. With just one handle, several bits can be conveniently installed to drive a variety of screws and types.
With bits, you do not need to carry too many screwdrivers to accomplish a job. Just a collection of interchangeable tips, made of extra tough materials, does the trick. A bit, selected to fit a driving surface, becomes a part of the screwdriver to transfer the applied force for tightening or freeing-up of a screw. The main benefit lies in close packing these bits, according to ascending or descending order, of length and screw types, to save on the precious space for tools available to a work-person.
The screwdriver depends on the screw-type. Initially, screws with slotted or blade style screw head configurations were employed those were easy to produce. However, with the advent of power drills, it became feasible to pre-drill holes that revolutionize the field. Socket-head screws made its way with the turn of the twentieth century. The use socket-head screws rapidly grew in popularity. In the late thirties, the screw heads with a deep socket with a cruciform slot quickly became popular due to its rigidity and resistance to wear and tear. This design, known as Phillips®, became indispensable with self-centering characteristics, to the auto industry. This particular type of screw head and others like the square, hex, and Torx designs are also in vogue. The power tools with a grip that slides at a preset torque enable to tighten screws without damaging or over-tightening.
Screwdrivers are available in manual, electric or pneumatic types to power the bit. There are torque screw drivers to tighten screws to a specified torque and available in cordless variety also. Powered screwdrivers commonly use electric or air motor with speed and torque switch. Interchangeable hardened bits with powered screwdrivers, help increase the efficiency of work. Some screwdrivers come with ratchet action whereby it only allows the clockwise rotation and gets uncoupled for anti-clockwise rotation for tightening of screws and vice-versa for loosening.
It is essential to select a drive type bit for a particular drive design to match your application. Phillips® driver remains the most common head types and available as driver bits in a variety of lengths, arbitrarily identified by a number such as P2. It remains immensely popular in manufacturing industries as it meets needs of slot-driven screws, cam out (when rotational force of a bit causes to disengage the fastener and slips out, affecting its life cycle), self-alignment and resistance to power tools. Square Drive allows easy insertion of the device while the screw is held in place without difficulty. The main advantage with a Square drive bit lies in the ease of removing the screw, even if it is painted over. This screw drive type bits are in demand for decking and timber casing. Hex (socket) drive with a hexagonal recess, requires to be driven by a compatible bit, and Torx (star-drive) with a hexagonal bit allows increased torque transfer from the driver to the bit with relative ease. It saves you from undue fatigue.