Locknuts are used to create a more secure hold for screws and bolts. Two different types of hardware actually fall under the definition of "lock nut." The first and most common type of locknut is a nut which provides some sort of extra resistance to vibration. This resistance can come from a prevailing torque provided by the nut as well as some mechanical means of deforming or biting into the bolt. The other type of locknut is a small nut that tightens beneath the bigger primary nut in order to tighten it. Many different specifications exist to help make selecting locknuts easier.
Thread direction is quite simple, referring to the direction in which the nut tightens and loosens. Two types exist, left-hand nuts and right-hand nuts. Right-hand nuts tighten in a clockwise directions, and left hand nuts tighten in a counterclockwise direction.
The dimensions of a locknut are very important so that they can be matched to bolts and screws which they will tighten properly. The major dimensional measurements of locknuts include locking face diameter, overall locknut diameter and locknut width. Measurements are in either metric or English units.
The locking style of the nut is probably the most important of a locknut's specification. This refers to the way in which the nut manages to minimise movement in the nuts. Resilient ring locknuts have a durable material of some sort in between the threads, which causes the locking in the nut. The material is usually nylon, but also other materials occasionally appears. Setscrews attach to the locknut's periphery and distort the threads. Clamping screws have an entire clamping and locking section that are separated by a radial grove. Several other types of locking styles are also used.
Thread type is an important specification for locknuts. The main types of screw threads are metric, Whitworth, unified and high-tension. Locknuts come and are available in all of these threads.
The material from which a locknut is made is another important specification. Most often, these nuts are manufactured from a type of steel. The most common types of steel that make up locknuts are stainless steel, hardened alloy steel or heat-treated alloy steel.