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A nut is a type of fastener with a threaded hole. Nuts are almost always used in conjunction with a mating
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to fasten multiple parts together. The two partners are kept together by a combination of their threads' friction (with slight elastic deformation), a slight stretching of the bolt, and compression of the parts to be held together. In applications where vibration or rotation may work a nut loose, various locking mechanisms may be employed: lock washers, jam nuts, eccentric double nuts, specialist adhesive thread-locking fluid such as
Loctite Loctite is an American brand of adhesives, sealants, surface treatments, and other industrial chemicals that include acrylic, anaerobic, cyanoacrylate, epoxy, hot melt, silicone, urethane, and UV/light curing technologies. Loctite products ar ...
, safety pins (
split pins A brass fastener, butterfly clips, brad, paper fastener or split pin is a stationery item used for securing multiple sheets of paper together. A patent of the fastener was issued in 1866 to George W McGill. The fastener is inserted into punched ...
) or
lockwire Safety wire or locking-wire is a type of '' positive locking device'' that prevents fasteners from falling out due to vibration and other forces. The presence of safety wiring may also serve to indicate that the fasteners have been properly tigh ...
in conjunction with castellated nuts, nylon inserts (
nyloc nut A nyloc nut, also referred to as a nylon-insert lock nut, polymer-insert lock nut, or elastic stop nut, is a kind of locknut with a nylon collar that increases friction on the screw thread. The nylon collar insert is placed at the end of the nut, ...
), or slightly oval-shaped threads. Square nuts, as well as bolt heads, were the first shape made and used to be the most common largely because they were much easier to manufacture, especially by hand. While rare today due to the reasons stated below for the preference of hexagonal nuts, they are occasionally used in some situations when a maximum amount of torque and grip is needed for a given size: the greater length of each side allows a spanner to be applied with a larger surface area and more leverage at the nut. The most common shape today is hexagonal, for similar reasons as the bolt head: six sides give a good granularity of angles for a tool to approach from (good in tight spots), but more (and smaller) corners would be vulnerable to being rounded off. It takes only one sixth of a rotation to obtain the next side of the hexagon and grip is optimal. However, polygons with more than six sides do not give the requisite grip and polygons with fewer than six sides take more time to be given a complete rotation. Other specialized shapes exist for certain needs, such as wingnuts for finger adjustment and captive nuts (e.g. cage nuts) for inaccessible areas.


Types

A wide variety of nuts exists, from household hardware versions to specialized industry-specific designs that are
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to meet various technical standards. Fasteners used in automotive, engineering, and industrial applications usually need to be tightened to a specific torque setting, using a torque wrench. Nuts are graded with strength ratings compatible with their respective bolts; for example, an ISO property class 10 nut will be able to support the bolt
proof strength In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and wi ...
load of an ISO property class 10.9 bolt without stripping. Likewise, an SAE class 5 nut can support the proof load of an SAE class 5 bolt, and so on.


Locknuts

Many specialised types of nut exist to resist loosening of bolted joints, either by providing a prevailing torque against the male fastener or by gripping against the bolted components. These are generally referred to as locknuts. * Castellated nut *
Distorted thread locknut A distorted thread locknut,McMaster, p3139 is a type of locknut that uses a deformed section of thread to keep the nut from loosening from vibrations or rotation of the clamped item. They are broken down into four types: elliptical offset nuts, cen ...
** Centerlock nut **
Elliptical offset locknut A distorted thread locknut,McMaster, p3139 is a type of locknut that uses a deformed section of thread to keep the nut from loosening from vibrations or rotation of the clamped item. They are broken down into four types: elliptical offset nuts, cen ...
** Toplock nut *
Interfering thread nut An interfering thread nut is a type of locknut that has an undersized root diameter. This creates an interference between the nut Nut often refers to: * Nut (fruit), fruit composed of a hard shell and a seed, or a collective noun for dry and edib ...
**
Tapered thread nut An interfering thread nut is a type of locknut that has an undersized root diameter. This creates an interference between the nut Nut often refers to: * Nut (fruit), fruit composed of a hard shell and a seed, or a collective noun for dry and edib ...
* Jam nut *
Jet nut A jet nut,. also known as a k-nut,. is a special type of hex locknut that is commonly used in the aerospace and automotive racing industries.Smith, pp. 106–107. It has a flange on one end of the nut, the hex is smaller than a standard siz ...
(K-nut) *
Keps nut A Keps nut, (also called a k-lock nutMcMaster, p3125 or washer nut), is a nut with an attached, free-spinning washer Washer most commonly refers to: *Washer (hardware), a thin usually disc-shaped plate with a hole in the middle typically used ...
(K-nut or washer nut) with a star-type lock washer * Nyloc plate nut *
Polymer insert nut A nyloc nut, also referred to as a nylon-insert lock nut, polymer-insert lock nut, or elastic stop nut, is a kind of locknut with a nylon collar that increases friction on the screw thread. The nylon collar insert is placed at the end of the nut, ...
(Nyloc) *
Security locknut A security locknut . is a type of industrial fastener composed of two steel threaded parts: a nut body and an elliptical spring steel lock ring. Security locknuts are fastened onto a mating bolt to form a bolted joint. Forces of friction (with ...
*
Serrated face nut A serrated face nut is a locknut with ridges on the face of the nut that bite into the surface it is tightened against. The serrations are angled such that they keep the nut from rotating in the direction that would loosen the nut. Due to the serra ...
*
Serrated flange nut A flange nut is a nut that has a wide flange at one end that acts as an integrated washer. This serves to distribute the pressure of the nut over the part being secured, reducing the chance of damage to the part and making it less likely to loosen ...
*
Speed nut A speed nut, aka sheet metal nut or Tinnerman nut, is a type of locknut with two sheet metal prongs that act as one thread. They are made from spring steel. The fastener serves the functions of both a lock washer and a nut. As the fastener i ...
(Sheet metal nut or Tinnerman nut) *
Split beam nut A split beam nut, also known as a split hex nut. or slotted beam nut, is a locknut with slots cut in the top that separate the outside end into two. or more sections that are bent slightly inward, making the thread diameter undersized in the slotted ...
* BINX nut.


Gallery

File:nut-hardware.jpg, Left to right: Wing, hex, hex flange, and slab weld nuts. File:Nut2-hardware.jpg, Left to right: Slotted, square (upper), T-nut (lower), cap (or acorn), nylon locking (top and side views), and castellated nuts. File:Hexagon nuts.jpg, Hexagon nuts.


Standard nut sizes


Metric hex nuts

Note that flat (spanner or wrench) sizes differ between industry standards. For example, spanner or
wrench size Width across flats is the distance between two parallel surfaces on the head of a screw or bolt, or a nut, mostly for torque transmission by positive locking. The term width across flats (AF) is used for the following forms: * 2-socket = round ...
s of fastener used in Japanese built cars comply with JIS automotive standard.


SAE hex nuts


Classifications


Manufacture

File:Screw (bolt) 17-n.PNG, Nut blanking File:Screw (bolt) 18-n.PNG, Nut threading


See also

* Bolted joint * Mechanical joint * Pipe cap * Tap * Tapped hole * Threaded insert *
Washer Washer most commonly refers to: *Washer (hardware), a thin usually disc-shaped plate with a hole in the middle typically used with a bolt or nut *Washing machine, for cleaning clothes Washer may also refer to: *Dishwasher, a machine for cleani ...


References


Bibliography

* . * {{Nuts (hardware) Threaded fasteners