A traditional screwdriver is a handheld device that relies on the effort of the user to rotate it while position it in the screw head. This effort moves the screw's spiral-threaded shank clockwise into the wood until the screw is flush with the surface, or rests against the item (bracket) being attached to the surface. Screwdrivers have three parts: the handle, the shank and the head.
The handle is the widest part of the screwdriver, cylindrically formed to fit comfortably in the hand. Some screwdriver handles are hexagonal or covered with a rubberized grip, to help stop the hand slipping while rotating the screwdriver. Manufacturers scientificaly design them to the correct diameter for maximum ease of use by the user, to insert the screw with a minimum amount of effort.
The shank is a lot thinner than the handle, usually roughly 1/3 inch thick. Generally made of hardened steel, it can be a few inches long to over a foot. These different lengths help insert screws that are easily accessible, or to insert in areas where hands are too large to be close to the screw.
The head -- or tip -- is on the end of the shank. This is the part of the screwdriver a worker inserts into the screw head. The head is generally hardened more so than the shank, as it is the only part of the screwdriver that moves against a hardened surface. Consequently, if the head breaks through after constant use, the rest of the screwdriver is redundant.
Types Of Screwdriver Heads
The most common types of screwdriver head are slotted (shaped like a thin wedge), or Philips (two slots centrally crossed at 90 degrees to each other). However, as there are many different designs of screw heads, there are many different screwdriver tips to accommodate them. Some of the different tips include Hex Key, Hex Head, Clutch head, Torx, Scrulox, Robertson, Quadrex, Pozidriv and Tri-Wing.