Description

Locknuts are a type of prevailing-torque fastener that resists loosening under vibration and torque. They differ from standard nuts because they typically have friction-increasing bearing surfaces (e.g., pitted grooves on flanges) or special internal thread-geometries. In addition to locknut type, these fasteners carry thread specifications and differ in terms of materials of construction, product features, and approvals. Locknuts are available in inch-based and metric designations, and have a numeric (e.g., # 1) or alphanumeric (e.g., M.2) description.

Types 

• Castle nuts are locknuts that have slots or notches that are cut into one end to allow a cotter pin or safety wire to assist in fastening. Castle nuts resemble a chess-playing piece and are also known as castellated or slotted locknuts.
• Distorted-thread locknuts use a deformed section of thread to prevent loosening due to vibration from or rotation of the clamped item. Categories include center-lock, elliptical-offset, top-lock, oval, and non-slotted hex.
• Flex-top locknuts or split-beam locknuts are made from a single piece of material and have a slotted top that expands as the nuts are tightened. This locks them into place and provides vibration resistance.
• Interfering threadnuts or tapered thread nuts are a type of locknut that has an over-sized root diameter to provide permanent or semi-permanent joining.
• Jam nuts are typically half the height of a standard nut. Often, these locknuts are pushed-up or jammed against a standard nut in a fastener assembly to provide an additional securing force.
• Jet nuts or K-nuts are smaller, flanged-type locknuts that are often used in aerospace or automotive racing applications.
• Speed nuts (sheetmetal nuts, tinnerman nuts) can be quickly pushed into place using deformable teeth instead of standard threads.
• Two-piece locknuts are sold as two-component, upper and lower nut assembly pairs. 

Specifications

• Thread direction - Locknuts are available with right-hand (clockwise) or left-hand (counterclockwise) threads.
• Construction material - Some are made of metal materials such as aluminum, brass, bronze, copper, steel, or titanium. They may be anodized, galvanized, nickel-plated, zinc-plated, or treated with other finishes. Non-metallic locknuts made of plastic, rubber, and nylon are also available.
• Non-integral hardware - Locknuts that are sold as an assembly have a non-integral or secondary-material hardware, typically a washer or plastic insert, to improve their mechanical performance. 

Standards

DIN 981 - Roller bearings - locknuts

References

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Altech Corp. | MISUMI USA | Fastener SuperStore, Inc.