Socket wrench

A socket wrench (or socket spanner) is a type of spanner (or wrench in North American English) that uses a closed socket format, rather than a typical open wrench/spanner to turn a fastener, typically in the form of a nut or bolt.

The most prevalent form is the ratcheting socket wrench, often informally called a ratchet. A ratchet incorporates a reversible ratcheting mechanism which allows the user to pivot the tool back and forth to turn its socket instead of removing and repositioning a wrench to do so.

Other common methods of driving sockets include pneumatic impact wrenches, hydraulic torque wrenches, torque multipliers and breaker bars. Some lesser known hybrid drivers include striking wrench tools with square drive, and hydraulic impact wrenches (typically powered by on site hydraulic power such as present with military tanks, and many rail car applications).

Interchangeable sockets

The basic contemporary form of socket is hexagonal, referred to as "6-point" for the pointed intersections where its six solid sided facets meet.

Male drivers are also produced for use with socket head cap screws, and are often called Allen drivers (trademark) or the generic term male bit drivers.

The principal advantage of interchangeable sockets is that, instead of a separate wrench for each of the many different fastener sizes and types, only separate sockets are needed for each size and type. Because of their versatility, nearly all screw and bolt types now have sockets of different types made to fit their bolts or nuts. Sockets often come as a "socket set" with many different sizes or types of sockets to fit the heads of different-sized fasteners. A ratchet of the "set size" is often included with the socket set. Sockets are commonly available in fractional inch and metric sizes, and in short (shallow) and longer (deep) varieties.