A nut is a type of

fastener A fastener (US English) or fastening (UK English) is a hardware device that mechanically joins or affixes two or more objects together. In general, fasteners are used to create non-permanent joints; that is, joints that can be removed or disman ...

with a threaded hole. Nuts are almost always used in conjunction with a mating

bolt The BOLT Browser was a web browser for mobile phones including feature phones and smartphones that can run Java ME applications. The BOLT Browser was offered free of charge to consumers and by license to mobile network operators and handset manuf ...

to fasten multiple parts together. The two partners are kept together by a combination of their threads'

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding (motion), sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative la ...

(with slight

elastic deformation In engineering, deformation refers to the change in size or shape of an object. ''Displacements'' are the ''absolute'' change in position of a point on the object. Deflection is the relative change in external displacements on an object. Stra ...

), a slight

stretching Stretching is a form of physical exercise in which a specific muscle or tendon (or muscle group) is deliberately flexed or stretched in order to improve the muscle's felt elasticity and achieve comfortable muscle tone. The result is a feelin ...

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 nut A jam nut is a low profile type of nut, typically half as tall as a standard nut. It is commonly used as a type of locknut, where it is "jammed" up against a standard nut to lock the two in place. It is also used in situations where a standard nu ...

s, 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 product ...

, safety pins ( split pins) or lockwire in conjunction with

castellated nut A castellated nut, sometimes referred to as a castle nut, is a nut with slots (notches) cut into one end. The name comes from the nut’s resemblance to the crenellated parapet of a medieval castle. Castellated nuts are sometimes referred to in ...

s, nylon inserts ( nyloc 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

hexagon In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A ''regular hexagon'' h ...

al, 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 nut A cage nut or caged nut (also called a captive or clip nut) consists of a (usually square) nut in a spring steel cage which wraps around the nut. The cage has two wings that when compressed allow the cage to be inserted into the square holes, ...

s) for inaccessible areas. SydneyHarbourBridgeNutMilsonsPoint

Types

A wide variety of nuts exists, from

household hardware Household hardware (or simply, hardware) is equipment that can be touched or held by hand such as keys, locks, nuts, screws, washers, hinges, latches, handles, wire, chains, belts, plumbing supplies, electrical supplies, tools, utensil ...

versions to specialized industry-specific designs that are engineered to meet various

technical standard A technical standard is an established norm or requirement for a repeatable technical task which is applied to a common and repeated use of rules, conditions, guidelines or characteristics for products or related processes and production methods, ...

s. Fasteners used in automotive, engineering, and industrial applications usually need to be tightened to a specific

torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of t ...

setting, using a

torque wrench A torque wrench is a tool used to apply a specific torque to a fastener such as a nut, bolt, or lag screw. It is usually in the form of a socket wrench with an indicating scale, or an internal mechanism which will indicate (as by 'clicking' ...

. 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 joint A bolted joint is one of the most common elements in construction and machine design. It consists of a male threaded fastener (e. g., a bolt) that captures and joins other parts, secured with a matching female screw thread. There are two main ty ...

s, either by providing a prevailing

against the male fastener or by gripping against the bolted components. These are generally referred to as locknuts. *

Castellated nut A castellated nut, sometimes referred to as a castle nut, is a nut with slots (notches) cut into one end. The name comes from the nut’s resemblance to the crenellated parapet of a medieval castle. Castellated nuts are sometimes referred to in ...

* Distorted thread locknut ** Centerlock nut ** Elliptical offset locknut ** 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 and the fastener, plastically deforming the threads Thread may refer to: Objects * Thread (yarn), a kind of thin y ...

** Tapered thread nut *

Jam nut A jam nut is a low profile type of nut, typically half as tall as a standard nut. It is commonly used as a type of locknut, where it is "jammed" up against a standard nut to lock the two in place. It is also used in situations where a standard nu ...

* Jet nut (K-nut) * Keps nut (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 * Serrated face nut * Serrated flange nut *

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 is ...

(Sheet metal nut or Tinnerman nut) * Split beam nut * 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 sizes 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

References

Bibliography

* . * {{Nuts (hardware) Threaded fasteners