Lock nut, jam nut 

What is a lock nut, a jam nut? A lock nut, also called a jam nut, is a special type of nut used in threaded connections to prevent the connection from loosening spontaneously. Its main function is to stabilize and secure the main nut or other threaded element against unwanted unscrewing, which can be caused by vibrations, load changes, or other mechanical factors. How does a lock nut work? A lock nut is tightened onto the thread after the main nut has been fixed. As a result: A mechanical lock is created that eliminates play between the threads. Frictional forces between the thread surfaces counteract the unscrewing of the nut under the influence of vibrations or loads. Lock nuts are used in systems where safety, stability, and durability of threaded connections are important. The English name for a przeciwnakrętka is LOCK NUT 

Why are lock nuts used?

They prevent unscrewing: Ideal for applications in difficult conditions, e.g., vibrations or variable loads. They stabilize connections: They keep elements in a fixed position. Simple installation: Easy to assemble and disassemble, making them a universal solution. Where are lock nuts used? Lock nuts are used, among others, in the following industries: Power hydraulics: For fixing bulkhead fittings and other elements in high-pressure installations, e.g. elbow fittings; Mechanics: In structures exposed to vibrations, e.g., industrial machines, vehicles. Pneumatic and water installations: They ensure stable connections in transmission systems.

Construction and types of lock nuts

• Standard lock nut: It is thinner than a regular nut and used in pairs with another nut.
• With a spring insert: It has an additional ring or insert, e.g., made of nylon, which increases friction and improves the stability of the connection.
• Jam nut with internal thread: Used in hydraulic or pneumatic systems for fixing elements such as bulkhead fittings.

Narrow nuts 

A narrow nut, or as others call it, a lock nut in power hydraulics has several applications. It can be used together with a fitting as an element pressing the seal. It is also used for fixing quick couplings to fixed elements, e.g., a loader. Made according to the Polish Standard: PN-65/M-73109. Lock nuts are available with imperial or metric threads. 

POLISH STANDARD for lock nuts PN-65/M-731091 

Subject of the standard. The subject of the standard are lock nuts used in threaded pipe connectors for nominal pressure up to 32 MPa. Material. Steel with tensile strength R_mnot less than 500 MPa (about 50 kG/mm ) and a clear yield point R_g not less than 260 MPa (about 2 26 kG/mm ). Execution. Machined. Metric thread of medium accuracy class 6H according to PN-70/M-021 13. Thread chamfer dimensions according to PN-74/M-82063. Standard creation date: Submitted by the Ministry of Heavy Industry, established by the Polish Committee for Standardization on June 30, 1965, as a mandatory standard in the scope of production from January 1, 1967 (Mon. Pol. No. 52/l 965 item 274)

Examples of metric lock nut designations: 

Low hexagonal nuts 

What are low hexagonal nuts? Low hexagonal nuts are hexagonal-shaped fasteners that perform the function of tightening and securing threaded connections. They are distinguished by a smaller height compared to standard hexagonal nuts, which is why they are used wherever space saving, low construction weight, or the necessity of making a connection in a limited space is important. Due to their construction, low hexagonal nuts are often also referred to as "jam nuts" because they can act as an additional securing element against the main nut's spontaneous unscrewing. They are used in many fields – from construction and steel structures, through automotive and precision mechanics, to power hydraulics and pneumatics. They are most commonly produced from carbon steel, stainless steel, or brass, and are also available in various strength classes (e.g., 04, 05, 8, 10).

Hydraulic lock nuts

Lock nuts are specialized fasteners that play an important role in power hydraulics, pneumatics, and other mechanical applications where durable and reliable security of threaded connections is necessary. The Hydron store offers a wide range of lock nuts in various sizes, so you can easily match them to your assembly and operational needs.

How does a jam nut work?

A jam nut, otherwise known as a lock nut, fulfills a stabilizing and securing function for threaded connections. In a typical application, the main hexagonal nut is tightened first, which carries the loads and connects the structural elements. Then, the jam nut is screwed onto the same thread and tightened against the main nut, which causes both nuts to lock each other and prevent spontaneous loosening. Such a solution is extremely useful in installations exposed to tremors, vibrations, and dynamic loads. The jamming function works thanks to the friction between the nut flanges and mutual pressure. After combining the main nut with the jam nut, a security effect is created that keeps the connection in a constant and stable position even in difficult working conditions.

Hexagonal nuts and their role

In a threaded system, the most commonly encountered elements are hexagonal nuts, which constitute the basic connecting element. Thanks to their hexagonal construction, they allow for easy tightening and unscrewing with an open-end or socket wrench, ensuring efficient transmission of axial and radial loads. Hexagonal nuts are designed with the transmission of internal forces of the threaded connection in mind, which makes them a structural element rather than just a securing one. It is they that maintain the compression between the connected elements, and their geometry ensures a large contact surface and appropriate load-bearing capacity.

Low nut – what characterizes it?

Lock nuts are classified as low nuts, i.e., elements with a reduced height compared to standard hexagonal nuts. The low construction is a deliberate technical solution that determines their application. Low nuts have a smaller height than classic structural nuts because their task is not to carry the main loads, but to press and lock an already existing threaded connection. The low height of the lock nut means that: it can be used in limited assembly spaces where a standard nut might not fit, it finds application as a securing and jamming element for connections without significantly increasing the thread length, it enables precise positioning of threaded elements, which is important in technical and hydraulic applications.

Application of lock nuts in power hydraulics

Lock nuts are particularly valued in hydraulic systems, where installations are exposed to high pressures, intense vibrations, and variable loads. They are used for: securing hydraulic fittings and quick couplings against loosening, immobilizing assembly elements in blocks, bodies, and manifolds, optimizing the durability and reliability of threaded connections in industrial machines and devices.

Why is it worth using lock nuts?

Introducing lock nuts into a set of fasteners is a solution that significantly increases the safety and reliability of connections. Thanks to them, it is possible to reduce the risk of elements loosening even under intense working conditions. Jam nuts are simple to install, universal, and used in many branches of industry. As a company with many years of experience in the power hydraulics industry, Hydron offers a wide selection of lock nuts made of high-strength materials and protected with anti-corrosion coatings. Our products are characterized by reliability, proven performance, and are eagerly chosen by professionals looking for durable solutions. We invite you to familiarize yourself with the offer of lock nuts in our store and to contact our team, who will be happy to advise you on choosing the optimal elements for your application.