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 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 in ...

* Distorted thread locknut ** Centerlock nut ** Elliptical offset locknut ** Toplock nut ** Philidas 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 that resists loosening under vibrations and torque. Prevailing t ...

** 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 nut ...

* Jet nut (K-nut). * Keps nut (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 p ...

* 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 e ...

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

Serrated face nut A serrated face 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 that resists loosening under vibrations and torque. Prevailing torque nuts ha ...

* 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 loose ...

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 ...

(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 tight ...

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 ( Bellev ...

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 t ...

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)