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 * 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 ** Philidas nut * Interfering thread nut ** Tapered thread nut * Jam 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 * 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 All steel reusable nut for high vibration and harsh environments. * 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.) * Eccentric double nut 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 (fastener), bolt) that captures and joins other parts, secured with a matching female screw thread. Ther ...

. Other methods include safety wire, lock washers, and thread-locking fluid.

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)