Bahco Socket Sets

A socket wrench is a wrench with interchangeable heads called sockets that attach to a fitting on the wrench, allowing it to turn different sized bolts and other fasteners. The most common form is a hand tool popularly called a ratchet consisting of a handle with a ratcheting mechanism built in, so it can be turned using a back-and-forth motion in cramped spaces. A socket has a cup-shaped fitting with a recess that grips the head of a bolt. The socket snaps onto a male fitting on the handle. The handle supplies the mechanical advantage to provide the torque to turn the socket. The wrench usually comes in a socket set with many sockets to fit the heads of different-sized bolts and other fasteners. The advantage of a socket wrench is that, instead of a separate wrench for each of the many different bolt heads used in modern machinery, only a separate socket is needed, saving space.
The socket wrench typically is of the ratchet type. The ratcheting mechanism allows the nut to be tightened or loosened with a reciprocating motion, without requiring that the wrench be removed and refitted after each turn. Typically, a small lever on the ratchet head switches the wrench between tightening and loosening mode. The sockets are attached to the ratchet through a square fitting that contains a spring-loaded ball detent mechanism to keep the sockets in place. These drive fittings come in four common sizes: 1/4 inch, 3/8 inch, 1/2 inch, and 3/4 inch (referred to as drives, as in "3/8 drive"). Despite being denominated in inches, these are international standards and no metric counterparts exist. Larger drive sizes such as 1 inch and above are usually reserved for use on fasteners of larger industrial equipment, such as tractor-trailers (articulated lorries), large cargo aircraft and passenger airliners, and marine work (merchant fleets, navies, shipyards). The sockets themselves come in a full range of inch and metric sizes. ("SAE" is often used as a blanket term for the nonmetric sizes, despite the technical inaccuracy of that usage.) The advantages of the system of a ratchet wrench with indexable sockets are speed of wrenching (it is much faster than a conventional wrench, especially in repetitive bolt-on or bolt-off usage) and efficiency of tooling cost and portability (it is much more efficient than a set of nonratcheting wrenches, with every size head having its own handle).info supplied by Wikipedia.