Socket wrench
Encyclopedia
Wrench
A wrench or spanner is a tool used to provide grip and mechanical advantage in applying torque to turn objects—usually rotary fasteners, such as nuts and bolts—or keep them from turning....
with interchangeable heads called sockets that attach to a fitting on the wrench, allowing it to turn different sized bolt
Bolt
-Fasteners:*A cap screw, as used in a bolted joint*Screw, a cylindrical threaded fastener*Dead bolt, a kind of locking mechanism*Bolt , an anchor point used in rock climbing-Weaponry:*Bolt , a mechanism used in firearms...
s and other fasteners. The most common form is a hand tool
Hand tool
A hand tool is a device for performing work on a material or a physical system using only hands. The hand tools can be manually used employing force, or electrically powered, using electrical current...
popularly called a ratchet consisting of a handle with a ratcheting mechanism
Ratchet (device)
A ratchet is a device that allows continuous linear or rotary motion in only one direction while preventing motion in the opposite direction. Because most socket wrenches today use ratcheting handles, the term "ratchet" alone is often used to refer to a ratcheting wrench, and the terms "ratchet"...
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
Gender of connectors and fasteners
In electrical and mechanical trades and manufacturing, each half of a pair of mating connectors or fasteners is conventionally assigned the designation male or female...
fitting on the handle. The handle supplies the mechanical advantage
Mechanical advantage
Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Ideally, the device preserves the input power and simply trades off forces against movement to obtain a desired amplification in the output force...
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 other common form factor is a power tool
Power tool
A power tool is a tool that is actuated by an additional power source and mechanism other than the solely manual labour used with hand tools. The most common types of power tools use electric motors. Internal combustion engines and compressed air are also commonly used...
version in which a socket set is used with an impact wrench
Impact wrench
An impact wrench is a socket wrench power tool designed to deliver high torque output with minimal exertion by the user, by storing energy in a rotating mass, then delivering it suddenly to the output shaft.Compressed air is the most common power source, although electric or hydraulic...
. The wrench is usually powered pneumatically
Pneumatics
Pneumatics is a branch of technology, which deals with the study and application of use of pressurized gas to effect mechanical motion.Pneumatic systems are extensively used in industry, where factories are commonly plumbed with compressed air or compressed inert gases...
, although electric versions are not uncommon. Hydraulic motor
Hydraulic motor
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement . The hydraulic motor is the rotary counterpart of the hydraulic cylinder....
versions are rare outside of heavy industry. The sockets for impact duty (called impact sockets) are made with higher bulk and strength than those for hand-tool duty. They are typically finished in black oxide
Black oxide
Black oxide or blackening is a conversion coating for ferrous materials, copper and copper based alloys, zinc, powdered metals, and silver solder. It is used to add mild corrosion resistance and for appearance. To achieve maximum corrosion resistance the black oxide must be impregnated with oil or...
rather than the chrome plating
Chrome plating
Chrome plating, often referred to simply as chrome, is a technique of electroplating a thin layer of chromium onto a metal object. The chromed layer can be decorative, provide corrosion resistance, ease cleaning procedures, or increase surface hardness.-Process:A component to be chrome plated will...
typical of the hand-tool variety.
The principal application of socket wrenches is to loosen and tighten fasteners such as nut
Nut (hardware)
A nut is a type of hardware fastener with a threaded hole. Nuts are almost always used opposite a mating bolt to fasten a stack of parts together. The two partners are kept together by a combination of their threads' friction, a slight stretch of the bolt, and compression of the parts...
s and bolts.
Nut driver
Nut driver
A nut driver is a tool for tightening nuts and bolts. It essentially consists of a socket attached to a shaft and cylindrical handle and is similar in appearance and use to a screwdriver. They generally have a hollow shaft to accommodate a shank onto which a nut is threaded...
s also use a female socket to envelop and drive a male fastener head. From an etic
Emic and etic
Emic and etic are terms used by anthropologists and by others in the social and behavioral sciences to refer to two kinds of data concerning human behavior...
perspective they are a variation of the socket-as-wrench theme, but they are not emically classified in English by the name "socket wrench".
Description
The socket wrench typically is of the ratchet type. The ratchetRatchet (device)
A ratchet is a device that allows continuous linear or rotary motion in only one direction while preventing motion in the opposite direction. Because most socket wrenches today use ratcheting handles, the term "ratchet" alone is often used to refer to a ratcheting wrench, and the terms "ratchet"...
ing 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
Ball detent
A ball detent is a simple mechanical arrangement used to hold a moving part in a temporarily fixed position relative to another part. Usually the moving parts slide with respect to each other, or one part rotates within the other....
mechanism to keep the sockets in place. These drive fittings come in four common sizes: 1/4 inch
Inch
An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...
, 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
Metre
The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...
counterparts exist. Larger drive sizes such as 1 inch and above are usually reserved for use on fastener
Fastener
A fastener is a hardware device that mechanically joins or affixes two or more objects together.Fasteners can also be used to close a container such as a bag, a box, or an envelope; or they may involve keeping together the sides of an opening of flexible material, attaching a lid to a container,...
s of larger industrial equipment, such as tractor-trailers
Semi-trailer truck
A semi-trailer truck, also known as a semi, tractor-trailer, or articulated truck or articulated lorry, is an articulated vehicle consisting of a towing engine , and a semi-trailer A semi-trailer truck, also known as a semi, tractor-trailer, or (in the United Kingdom and Ireland) articulated truck...
(articulated lorries), large cargo aircraft and passenger airliner
Airliner
An airliner is a large fixed-wing aircraft for transporting passengers and cargo. Such aircraft are operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an aircraft intended for carrying multiple passengers in commercial...
s, and marine work (merchant fleets
Ship transport
Ship transport is watercraft carrying people or goods . Sea transport has been the largest carrier of freight throughout recorded history. Although the importance of sea travel for passengers has decreased due to aviation, it is effective for short trips and pleasure cruises...
, navies
Navy
A navy is the branch of a nation's armed forces principally designated for naval and amphibious warfare; namely, lake- or ocean-borne combat operations and related functions...
, shipyard
Shipyard
Shipyards and dockyards are places which repair and build ships. These can be yachts, military vessels, cruise liners or other cargo or passenger ships. Dockyards are sometimes more associated with maintenance and basing activities than shipyards, which are sometimes associated more with initial...
s). The sockets themselves come in a full range of inch and metric sizes. ("SAE
SAE International
SAE International is an organization for engineering professionals in the aerospace, automotive, and commercial vehicle industries. The Society is a standards development organization for the engineering of powered vehicles of all kinds, including cars, trucks, boats, aircraft, and others.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).
History
Scientific American
Scientific American is a popular science magazine. It is notable for its long history of presenting science monthly to an educated but not necessarily scientific public, through its careful attention to the clarity of its text as well as the quality of its specially commissioned color graphics...
Patent Agency on June 18, 1863. The first illustration of the tool appears on pg. 248 of the April 16, 1864 issue of Scientific American.
Square heads and sockets were the easiest to make in the era when hand filing
File (tool)
A file is a metalworking and woodworking tool used to cut fine amounts of material from a workpiece. It most commonly refers to the hand tool style, which takes the form of a steel bar with a case hardened surface and a series of sharp, parallel teeth. Most files have a narrow, pointed tang at one...
was the typical method of manufacture. With the proliferation of modern manufacturing methods, such as milling
Milling machine
A milling machine is a machine tool used to machine solid materials. Milling machines are often classed in two basic forms, horizontal and vertical, which refers to the orientation of the main spindle. Both types range in size from small, bench-mounted devices to room-sized machines...
, shaping
Shaper
A shaper is a type of machine tool that uses linear relative motion between the workpiece and a single-point cutting tool to machine a linear toolpath. Its cut is analogous to that of a lathe, except that it is linear instead of helical...
, broaching, and advanced die
Die (manufacturing)
A die is a specialized tool used in manufacturing industries to cut or shape material using a press. Like molds, dies are generally customized to the item they are used to create...
forging, 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. Of course, 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.
Number of points
Modern nuts and bolt heads are made with hexagonal gripping surfaces and as such limit the number of positions a wrench can adopt when placed over them. Sockets are produced in 6-point (hexagonal), 8 point, and 12-point (double-hexagonal) configurations. 12-point sockets can be used on square nuts and fasteners, and also offer double the amount of starting points. Due to the twisting or cam action of the socket, most of the torque is applied at or near near the corners of the fastener head, so that greater torque can be achieved with 12 point fastener heads. Some assert that 12 -point sockets are more likely to round the points of a fastener than a 6-point socket, but since the torque is applied at the points of the fastener, there is no measurable difference between the two for a given fastener head. In general, 12-point sockets, being faster and more versatile, are used in general purpose applications. Impact sockets are usually 6-point sockets, as the 6-point design allows for a thicker, stronger socket wall with less increase in the outside diameter of the socket.8-point sockets are still available from some manufacturers, allowing socket users to adjust square-shaped fittings rather than hexagonal ones. They were much more easily available some years ago, but square-head bolts and nuts, once common, have become a rarity in modern toolmaking.
Shallow vs deep
Some high-end manufacturers, such as Snap-on
Snap-on
Snap-on is a leading US designer, manufacturer and marketer of tools and equipment to professional tool users. It was founded in 1920. Snap-on is located in Kenosha, Wisconsin, and employs approximately 11,500 people worldwide...
or Mac Tools
Mac Tools
Mac Tools is a professional tool company located in Westerville, Ohio, USA. The Mac Tools line consists of over 8000 professional tools including screwdrivers, ratchets, wrenches, and assorted air tools. Mac Tools also makes its own tool boxes located in its manufacturing plant in Georgetown, Ohio...
, offer what are called "semi-deep" or "mid-length" sockets, which provide much of a deep socket's depth, while fitting in tighter locations.
Impact sockets
High strength fasteners in demanding situations often require the use of an impact wrenchImpact wrench
An impact wrench is a socket wrench power tool designed to deliver high torque output with minimal exertion by the user, by storing energy in a rotating mass, then delivering it suddenly to the output shaft.Compressed air is the most common power source, although electric or hydraulic...
or impact driver
Impact driver
An impact driver is a tool that delivers a strong, sudden rotational and downward force. In conjunction with toughened screwdriver bits and socket sets, they are often used by mechanics to loosen larger screws and nuts that are corrosively "frozen" or over-torqued...
to deliver the amount of torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
required to tighten or loosen them. Standard sockets are made of a strong, but brittle steel, such as chrome
Chromium
Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
steel. When used with an impact wrench they can shatter explosively if they break. Impact sockets are made of a weaker, but thicker and more malleable steel that will deform and split instead of shattering, such as chrome molybdenum
Molybdenum
Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
steel. These sockets are not chrome-plated
Chrome plating
Chrome plating, often referred to simply as chrome, is a technique of electroplating a thin layer of chromium onto a metal object. The chromed layer can be decorative, provide corrosion resistance, ease cleaning procedures, or increase surface hardness.-Process:A component to be chrome plated will...
, as chrome can chip when used with impact wrenches. Instead, they are made with a coating of black oxide
Black oxide
Black oxide or blackening is a conversion coating for ferrous materials, copper and copper based alloys, zinc, powdered metals, and silver solder. It is used to add mild corrosion resistance and for appearance. To achieve maximum corrosion resistance the black oxide must be impregnated with oil or...
or a plastic coating to prevent corrosion. Although ordinary sockets should not be used with impact wrenches, impact sockets can be used with hand socket wrenches and other hand drivers. In some breaker bar
Breaker bar
A breaker bar is a long non-ratcheting bar that is used with socket wrench style sockets. Breaker bars are used to 'break loose' very tight fasteners because their additional length allows the same amount of force to generate significantly more torque than a standard length socket wrench. The use...
use, and especially in cheater bar
Cheater bar
A cheater bar or cheater pipe is an improvised breaker bar made from a length of pipe and a wrench .-Primary use:Cheater bars are usually used to free screws, bolts, and other fasteners that are difficult to remove with a ratchet or wrench alone...
use (which is usually ill-advised anyway), a user may feel safer using an impact socket.
Accessories
These are some of the common accessories that are used with socket wrenches:- Extensions, sometimes called "extender arms", allow access to nuts that are difficult to reach, typically in automotive applications.
- A breaker barBreaker barA breaker bar is a long non-ratcheting bar that is used with socket wrench style sockets. Breaker bars are used to 'break loose' very tight fasteners because their additional length allows the same amount of force to generate significantly more torque than a standard length socket wrench. The use...
is an extended-length handle for sockets that adds extra torque for loosening strongly tightened or frozen fasteners. - Universal joints are two articulated socket joints combined at a right angle, that allow a bend in the turning axis of the wrench. They are used with extensions for turning a bolt or nut at a difficult to access location.
- Flex handles are socket wrenches in which the drive head pivots back and forth on the handle, to allow the handle to avoid obstructions when being turned in a cramped space.
- Adapters allow sockets of one drive size to be used with wrenches of another drive size. They consist of a male drive fitting of one size attached to a female drive fitting of another size. For example, a 1/4 in. to 3/8 in. adapter allows sockets with 1/4 in. drive holes to attach to 3/8 in. wrenches.