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 Nut often refers to: * Nut (fruit), fruit composed of a hard shell and a seed, or a collective noun for dry and edible fruits or seeds * Nut (hardware), fastener used with a bolt Nut or Nuts may also refer to: Arts, entertainment, and media Co ...

that resists loosening under vibrations and torque. Prevailing torque nuts have some portion of the nut that deforms elastically to provide a locking action. Free-spinning locknuts exist which carry the advantage of not requiring extra torque until seated.

Types

There are various kinds of specialised lock nuts, including: *

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 inc ...

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 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 ...

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 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 ...

Philidas nut Philidas Ltd. (previously named Infast Philidas) is a company based in Pontefract, West Yorkshire, England that manufactures nuts and components for automotive and industrial applications. History The company was established in 1942, and is a b ...

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 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 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 free-spinning washer. In the locknut form, this is a star-type lock washer. *

Plate nut A plate nut, also known as a nut plate, anchor nut or anchor plate, is a stamped sheet metal nut that is usually riveted to a workpiece. They have a long tube that is internally threaded and a plate with two clearance holes for rivets. The most popu ...

* Polymer insert nut (

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, ...

) *

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 ...

All steel reusable nut for high vibration and harsh environments. *

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.) *

Eccentric double nut Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

A free spinning locknut composed of two nuts, one with a protruding section, one with a recessed section.

Prevailing torque values

''Prevailing torque'' differentiates a locknut from a free spinning nut based on a value of how much torque is required during installation before clamp loading. For example, on a nylon-insert nut, it is the torque needed to overcome the resistance of the nylon dragging across the mating thread. This torque value is usually not very high relative to final installation torque. Tolerance ranges for torque are specified in some standards such as (ISO, DIN, IFI, ASME, SAE, AN-, MS-, NAS- NASM-).

Prevention of loosening

Locknuts are one way to prevent vibration from loosening a

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 t ...

. Other methods include

safety wire 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 ...

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 ...

s, and

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 the ...

References

Notes

Bibliography

External links

"Hold Everything", February 1946, ''Popular Science''
page on lock nuts and washer technology developed during World War Two {{Nuts (hardware) Nuts (hardware)