Socket wrench

(above), four hex sockets and a universal joint 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).

(above), four hex sockets and a universal joint]] 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).

History

Wrenches in the form of sockets—that is, a female driver to envelop the male head of a fastener—have existed for centuries. Early examples include the keys used to wind clocks since the Middle Ages. The heads and sockets were typically square; hex heads eventually became more common starting in the 20th century. The ratcheting socket wrench, with interchangeable (indexable) sockets, was invented by an American, J.J. Richardson, of Woodstock, Vermont. The tool was patented ( ) through the Scientific American Patent Agency on June 16, 1863. The first illustration of the tool appears on p. 248 of the April 16, 1864 issue of Scientific American. In current American English usage, the term "socket wrench" describes the wrench, not the socket. However, the term "socket wrench" is not used in British English. 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 and patented in 1964 ( ) by Peter M. Roberts.

Related tools

Fixed socket

Socket types

There are two main types of sockets: impact and hand. Sockets are referred by their number of “points” for the pointed intersections of their multi-faceted interior sides. Common designs include: 6 point, hexagon, for hexagonal nuts. Variants include designs with curved (splined) faces for off nut corner contact, to reduce chance of stripping 12 point (24 facets) for use with hexagonal nuts 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. A much rarer form of socket is the penta socket, or 5 point socket, used with things such as, Telephone lines, waterworks, and certain vehicles. By far the most common use for them is with water meters, which have 5 sided bolts or nuts.

Impact sockets and drivers

Sockets for use with an impact wrench or impact driver are expected to receive higher torques, which is also percussive, and so need to be made of tougher materials. They are made from a thicker, tougher and more ductile alloy steel, often using CrMo steel to replace the CrV steel used in non-impact sockets. Most impact sockets made for "standard" hexagonal fasteners have a six-point design. 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.

Standard-length and deep-length sockets

Sockets are available in various depths or lengths, often divided by most manufacturers into two categories of "standard" and "deep" according to the ANSI or DIN standard they are made to and the tolerances allowed by those specifications for each length of socket. Because the standards allow for some flexibility in tolerances, it is common to see two manufacturers make deep sockets of the same size but with slightly different depths even though both meet the same specification. Standard length, otherwise known as "shallow" sockets, have a lower profile and allow a user to access nuts in narrow spaces. Deep sockets are useful for turning nuts onto bolts when the bolt extends upwards into the socket (as in the case of many bolted joints), a very typical example being exhaust clamp bolts on a car. Low-profile sockets, shorter even than standard sockets, are available for some applications, typically oil filter removal on engines with limited access. 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.

Pass-through sockets and ratchets

Some sockets are designed to have the same outside diameter and shape within a given set size. Each pass-through socket, within a given socket set, is designed to be used with a "special" ratchet that fits on the outside of the socket and not to the middle of the socket. By fitting the outside of the socket they allow the bolt or stud to extend through the socket, eliminating the need for a deep socket in some applications. By attaching to the outside of the socket they also allow the socket to be built up to 50% shorter and with 20% less width which is an advantage in some situations. Pass-through sockets and ratchets are built for -inch, -inch and -inch sets in both SAE and metric sizes. By using a fine tooth ratchet and socket system that allow a pass-through ratchet to be used as a conventional ratchet handle with interchangeable -inch and -inch drives some ratchets can be used with standard sockets. They are built by a number of manufacturers with a variety of trade names. Craftsman Tools call theirs Max Axess, and also sells GearWrench's Pass-Thru brands. Lowes calls their socket system Xtreme Access, etc.. Ratcheting box end wrenches can often be employed in the same application, but will nearly always be significantly wider.

Drivers

Male bit drivers are sometimes incorrectly referred to as "sockets", but are in fact the opposite of a socket - a socket is a female recess or opening which receives another object. Common male bit drivers of this type include Allen hex wrenches (in both metric and fractional inch sizes), Torx (T-3 through T-50) spline wrenches, 4-point (square), and 12-point (triple square) male bit drivers. Other specialized screw heads that are often installed or removed with screwdriver type handles and appropriate type tip have socket varieties that fit the various screw head types and a can be attached to a socket wrench. Conversely, for low torque situations, a "socket spinner" screwdriver handle with a socket wrench type fitting on one end can be attached to many different types of sockets, bit drivers and extensions.

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