220px-Screw Driver display

A flat-blade screwdriver


A screwdriver is a tool for driving screws and rotating other machine elements with the mating drive system. The screwdriver is made up of a head or tip, which engages with a screw, a mechanism to apply torque by rotating the tip, and some way to position and support the screwdriver. A typical hand screwdriver comprises an approximately cylindrical handle of a size and shape to be held by a human hand, and an axial shaft fixed to the handle, the tip of which is shaped to fit a particular type of screw. The handle and shaft allow the screwdriver to be positioned and supported and, when rotated, to apply torque. Screwdrivers are made in a variety of shapes, and the tip can be rotated manually or by an electric motor or other motor.

A screw has a head with a contour such that an appropriate screwdriver tip can be engaged in it in such a way that the application of sufficient torque to the screwdriver will cause the screw to rotate. If a screwdriver that is not the right size and type for the screw is 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, again to avoid damaging the screw.

220px-Jeweler's screwdriver

A jeweler's screwdriver

Lastly, screwdrivers come in a variety of sizes to match those of screws (i.e. jeweler's screwdrivers for tightening tiny eyeglass screws). In fact, all the very best screwdrivers have magnetic tips so the screws stay in place while using the tool. There is another tool used to magnetize and demagnetize drivers and is a must for any work shop.



List of common screwdriver heads. A. Slot screw B. Philips Screw

There are various types of screwdrivers; however,we'll discuss the the two-most common: flat-blade and Phillip heads.

First is the slot screw drive has a single slot in the fastener head and is driven by a flat-bladed screwdriver. The slotted screw is common in woodworking applications, but is not often seen in applications where a power tool would be used, due to the tendency of a power driver to slip out of the head and potentially damage the surrounding material. The tool used to drive a slot is called a slot-head, flat-tip, or flat head.

Secondly, Created by Henry F. Phillips, the Phillips screw drive was purposely designed to cam out when the screw stalled, to prevent the fastener damaging the work or the head, instead damaging the driver. This was due to the relative difficulty in building torque limiting into the early drivers.

The American Screw Company was responsible for devising a means of manufacturing the screw, and successfully patented and licensed their method; other screw makers of the 1930s dismissed the Phillips concept since it calls for a relatively complex recessed socket shape in the head of the screw — as distinct from the simple milled slot of a slotted type screw.

There are five relatively common (and two rather uncommon) Phillips drive sizes, which are different from the screw size; they are designated 000, 00, 0, 1, 2, 3, and 4 (increasing in size).