A socket wrench is a type of wrench Socket wrench: A wrench usually in the form of a bar and removable socket made to fit a bolt or nut Merriam-Webster (spanner in British English) that inserts into a socket to turn a fastener, typically in the form of a nut or bolt. “Socket wrench: A ratchet tool with a series of detachable sockets for tightening and loosening nuts of different sizes.“ Oxford Dictionaries
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).
The basic contemporary form of socket Is hexagonal, referred to as "6-point" for the pointed intersections where its six solid sided facets meet. These are attached to the driving tool via a male/female square connection fitting (called the square drive). Standard sizes of square drives around the world include , , , , 1, , and -inch square drive sizes (a de facto international standard with no metric equivalents) along with some lesser used drivers such as -inch square drive, and both No. 4 and No. 5 spline drives specified in ANSI B107 specifications. This wide range of square drive sizes provides for a wide variety of socket types and sizes to suit small to very large nuts and bolts. Some square drivers have a through hole to attach the socket to the driver (using a retaining ring with O-ring and pin type, or single piece molded retaining rings), a locking pin, or friction ball. Some common hand ratchets employ a quick release button on their top for quick socket release of smaller sockets. The tool chosen to drive the socket wrench ultimately supplies the mechanical advantage needed by the user to provide the torque needed to loosen or tighten the fastener as may be required. Larger drivers are typically used with higher torque, while smaller drivers are used for convenience in smaller low torque applications. Given the limits of human strength and fatigue, torque above 600 ft-lbs of torque will generally involve some kind of power assist, instead of the user simply pushing on the handle of a wrench. Very large sockets and drivers are typically powered by hydraulics to achieve torque.
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 inch and metric sizes, and in short (shallow) and longer (deep) varieties.
The first illustration of the tool appears on p. 248 of the April 16, 1864 issue of Scientific American. In current English usage, the term "socket wrench" describes the wrench, not the socket.
Square heads and sockets were the easiest to make in the era when hand filing was the typical method of manufacture. With the proliferation of modern manufacturing methods it became just as easy to make hex heads and sockets as square ones. The hex form allows easier wrenching in confined surroundings (where nearby obstacles obstruct the swing of the wrench), because fewer degrees of arc are needed on each swing before it is possible to reposition the wrench onto the next set of flats. Ratchet wrenches further reduce this problem, as the wrench need only swing as many degrees as it takes for the ratchet pawl to catch the next tooth.
The quick release feature common to ratchets was invented by Peter M. Roberts http://content.time.com/time/magazine/article/0,9171,946093,00.html
|A non-ratcheting socket wrench where the socket is attached permanently to the end of a L-shaped, or X-shaped bar. They are designed as special use socket wrenches for loosening and tightening lug nuts on automobile or truck wheels.|
|nut driver||A screwdriver-type handle for hand turning with a built-in female socket at the end of either metric or fractional inch sizes. May be of different lengths.|
|flex-head socket wrench|
|Combination wrenches with a fixed socket in place of the box end.|
|T-handle||A socket attached to a T-handle that is used for leverage. The socket may be fixed or sliding.|
|tuning wrench||Used to tune some musical instruments' strings.|
|spark plug wrench||A tube with six-sided sockets on both ends. It is turned with a short length of rod (Tommy bar or T-bar) inserted through two holes in the middle of the tube.|
|ratcheting socket wrench||The most common type of socket wrench. 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. These drive fittings come in four common sizes: inch, inch, inch, and inch (referred to as "drives", as in " drive"). Despite being denominated in inches, these are trade names (common product name), and manufacturers construct them to 6.3 mm, 9.5 mm, 12.5 mm and 19 mm, having been rounded to a reasonable, if haphazard, metric value. Larger drive sizes such as 1 inch and above are usually only encountered on of larger industrial equipment, such as tractor-trailers (articulated lorries), large cargo aircraft and passenger , and marine work (ship transport, navy, ). 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 non-ratcheting wrenches, with every size head having its own handle).
Fine-tooth ratchets have finer teeth on the ratcheting components; these can be useful for tighter locations. Dual-pawl ratchets click twice for each tooth on the gear, effectively doubling the granularity of the mechanism.
|click-style torque wrench||Normally ratcheting and click when a preset torque is reached. Some torque wrenches have digital read-outs of torque. Other types of torque wrenches exist such as torque limiting that only allow a preset torque to be reached before they slip. For some applications, torque multiplying devices are used with a torque wrench.|
|flex-head ratchet||Ratchets in which the drive head pivots or swivels back and forth on the handle at a pivot to the rear of the ratchet head.|
|Ratchets in which the entire ratchet head swivels with handle attachments on the side of the ratcheting head rather than the rear of the ratcheting head.|
|palm ratchet||Ratchets with a knurled palm sized circular ratchet handle with reversible socket attachment useful for rapidly loosening or tightening a bolt or nut. They come in a variety of sizes.|
|rotator ratchet||Allow the socket to be twisted by twisting the ratchet handle around the handle axis. Requires less than one degree arc swing to rotate socket, which makes them ideal for very tight spaces.|
|gearless ratchet||A ratchet that doesn't use gears, but instead uses bearings to provide virtually no arc swing nor produces an audible or discernible click.|
A number of other specialized ratchets—with hammer heads, multiple drive sizes, and other unusual features—are built by various manufacturers.
|A bar that attaches to a standard socket. Breaker bars are usually longer and built more sturdily than a standard ratchet handle and have a swiveling head that attaches to the socket. Breaker bars are used to break loose tight fasteners because their additional length and strength allows the same amount of force to generate significantly more torque than a standard length socket wrench. The use of a breaker bar also avoids potential damage to the ratcheting mechanism of a socket wrench. Once the fastener is "broken loose," it can be turned with a socket wrench or by hand.|
|beam-style torque wrench||Usually non-ratcheting, made to attach to standard sockets. By monitoring the degree of beam deflection, the applied torque can be determined.|
|A crank-shaped handle that rapidly loosens or tightens a fastener when used with the correct socket. It works much like a brace and bit adapted to sockets.|
|A screwdriver handle with a male drive end for attaching sockets.|
|offset drive||A fixed drive where the head spins relative to the handle spinning, with the handle having a drive attachment where a ratchet or other socket wrench can be attached.|
Less frequently used shapes include the square 4-point, triple square 12-point (not to be confused with 12-point double hexagon), octagonal 8-point (not to be confused with the more common 8-point double square shape). These less common shapes are typically found in special applications or particular industries such as aircraft, PVC plumbing fittings or German and UK made automobiles. With rail cars, valve adjustment screws and pipe plugs, the 4-point square shaped driver can still be found in wide use both male and female configurations. Nuts and bolt heads are also produced in 12-point double hexagon shapes and various types of splines, more common to aircraft and aerospace applications.
When working with common 6-point hexagonal fasteners, the 12-point shaped socket offers double the number of starting points or possible positions by which to put the socket on the nut, and so allows alignment every 30 degrees, rather than every 60 degrees of angle. Most manufacturers of sockets for larger hexagonal bolts produce them in 6-point (hexagonal) and limited sizes of 12-point (double-hexagonal) configurations.
Some specialized sockets are made with a specialized "6 flute" etc. socket that attaches to damaged bolts of both metric and fractional inch sizes for removal. Some specialized sockets are made to fit specific specialized applications and are designed and sized for that specific application. Spark plug sockets, oxygen sensor sockets, ball joint sockets, axle nut sockets, etc. fit in this category.
Chrome plated sockets are not suitable as the impact wrench may break the chrome plating, which can form razor sharp flakes - consequently impact sockets use different coatings - often a black phosphate conversion coating, or black oxide.
Although most manufacturers offer only those sizes and depths described within the common ANSI or DIN specifications, some exceptions do exist. Specialty manufacturers such as IMPERIAL-Newton Corp offer an expanded range of "extra deep" sockets for special industrial applications; and popular brands like Snap-on or Mac Tools offer what are called "semi-deep" or "mid-length" sockets, which provide much of a deep socket's depth, while fitting in tighter locations.