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 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 against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...

with slight

elastic deformation In engineering, deformation (the change in size or shape of an object) may be ''elastic'' or ''plastic''. If the deformation is negligible, the object is said to be ''rigid''. Main concepts Occurrence of deformation in engineering application ...

, a slight

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

of the bolt, and

compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression * Gas compression *Compression ratio, of a ...

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 washer A washer is a thin plate (typically disk-shaped, but sometimes square) with a hole (typically in the middle) that is normally used to distribute the load of a threaded fastener, such as a bolt or nut. Other uses are as a spacer, spring (Bellevil ...

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 Thread-locking fluid or threadlocker is a single-component adhesive, applied to the threads of fasteners such as screws and bolts to prevent loosening, leakage, and corrosion. Most thread-locking formulas are methacrylate-based and rely on t ...

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) or

lockwire A 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 tight ...

in conjunction with

castellated nut A castellated nut, sometimes referred to as a castle nut, is a nut with slots or 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 incorrectly re ...

s, 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

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 is de ...

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, f ...

s) for inaccessible areas. SydneyHarbourBridgeNutMilsonsPoint

History

Nuts and bolts were originally hand-crafted together, so that each nut matched its own bolt, but they were not interchangeable. This made it virtually impossible to replace lost or damaged fixers, as they were all different.

Joseph Whitworth Sir Joseph Whitworth, 1st Baronet (21 December 1803 – 22 January 1887) was an English engineer, entrepreneur, inventor and philanthropist. In 1841, he devised the British Standard Whitworth system, which created an accepted standard for screw ...

in 1841 proposed that a standard should be set, but it did not happen immediately. In 1851, the

Great Exhibition of the Works of Industry of All Nations The Great Exhibition of the Works of Industry of All Nations, also known as the Great Exhibition or the Crystal Palace Exhibition (in reference to the temporary structure in which it was held), was an international exhibition that took ...

was to be held in Hyde Park, London, England, and it was decided to build

the Crystal Palace The Crystal Palace was a cast iron and plate glass structure, originally built in Hyde Park, London, to house the Great Exhibition of 1851. The exhibition took place from 1 May to 15 October 1851, and more than 14,000 exhibitors from around ...

as part; this had to be done in 190 days, and at reasonable cost. Research into the remains of the destroyed building in 2024 revealed a major innovation that made this possible. The construction firm responsible, Fox Henderson, decided to use nuts and bolts, but to use standardised sizes, a revolutionary method at the time. This enabled the building to be completed in time. The use of interchangeable nuts and bolts was so successful that the Whitworth standard was widely adopted. A

British standard British Standards (BS) are the standards produced by the BSI Group which is incorporated under a royal charter and which is formally designated as the national standards body (NSB) for the UK. The BSI Group produces British Standards under th ...

was not formally adopted until 1905.

Types

There is a wide variety of nuts, from

household hardware Hardware (some types also known as household hardware) is equipment, generally used in machines, in construction or in any built good, that can be touched or held by hand such as keys, locks, nuts, screws, washers, hinges, latches, handles, wir ...

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

technical standard A technical standard is an established Social norm, 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 producti ...

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 analogue of linear force. It is also referred to as the moment of force (also abbreviated to moment). The symbol for torque is typically \boldsymbol\tau, the lowercase Greek letter ''tau''. Wh ...

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.

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 (fastener), bolt) that captures and joins other parts, secured with a matching female screw thread. Ther ...

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 or 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 incorrectly re ...

* Distorted thread locknut ** 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 due to vibrations, or rotation of the clamped item. There are four types: elliptical offset nuts, centerlock nuts ...

** Toplock nut *

Interfering thread nut An interfering thread nut is a type of locknut A locknut, also known as a lock nut, locking nut, self-locking nut, prevailing torque nut,. stiff nut or elastic stop nut, is a Nut (hardware), nut that resists loosening under vibrations and torq ...

** 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 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 (K-nut or washer nut) with a star-type lock washer * Nyloc plate nut * Polymer insert nut (Nyloc) *

Security locknut A security locknut . is a type of industrial fastener composed of two steel screw thread, threaded parts: a Nut (hardware), nut body and an elliptical spring steel lock ring. Security locknuts are fastened onto a mating bolt (fastener), bolt to fo ...

* 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 screw thread, thread. They are made from spring steel. Description The fastener serves the functions of both a lock washer and a ...

(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 A locknut, also known as a lock nut, locking nut, self-locking nut, prevailing torque nut,. stiff nut or elastic stop nut, is a Nut (hardware), nut that resists ...

* 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, wrench sizes of fastener used in Japanese built cars comply with JIS automotive standard.

SAE hex nuts

Classifications

Hex nuts, recognized by their six-sided shape, and square nuts, with a square form, are commonly used. Steel nuts are strong and great for construction, while

stainless steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...

ones resist rust, perfect for outdoor use. Brass nuts,

corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...

-resistant, find their place in electrical and plumbing work. Lock nuts, like nylon-insert or prevailing torque types, prevent loosening due to vibration or

, catering to specific needs across industries.

Manufacture

The manufacturing process of nuts involves several steps. It begins with the selection of

raw materials A raw material, also known as a feedstock, unprocessed material, or primary commodity, is a basic material that is used to produce goods, finished goods, energy, or intermediate materials/Intermediate goods that are feedstock for future finished ...

like steel, stainless steel, or brass, depending on the desired type of nut. The chosen material undergoes heating to make it more

malleable Ductility refers to the ability of a material to sustain significant plastic deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic deformation, which is reversi ...

, followed by forming or forging processes to create the basic shape of the nut. Threads are then cut or formed onto the nut using specialized machinery. After threading, nuts may undergo additional treatments such as

heat treatment Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are a ...

surface finishing Surface finishing is a broad range of industrial processes that alter the surface of a manufactured item to achieve a certain property. Finishing processes may be employed to: improve product appearance, adhesion or wettability, solderability, ...

to enhance their strength, durability, or appearance. Quality control checks are performed throughout the manufacturing process to ensure that the nuts meet industry standards and specifications. File:Screw (bolt) 17-n.PNG, Nut blanking File:Screw (bolt) 18-n.PNG, Nut threading

References

Bibliography

* . * {{Nuts (hardware) Threaded fasteners