What Is a Prevailing Torque Lock Nut? Working Principle, Types and Industrial Applications

Prevailing Torque Lock Nut

A prevailing torque lock nut is a type of self-locking fastener designed to resist loosening under vibration and dynamic loads. Unlike standard nuts, it maintains friction within the threads to provide consistent anti-loosening performance. These industrial fasteners are widely used in automotive, machinery, and structural applications.

Prevailing torque lock nuts are fasteners that use a locking mechanism to keep the nut from becoming free due to vibration or other forces. This nut is made to resist loosening even when subjected to repeated hits or vibrations. The nut's locking feature provides friction between the threads, preventing it from backing off. There are two standard torque lock nuts types: all metal and nylon inserts. To provide resistance against loosening, all metal dominant torque lock nuts employ a mechanical interference approach such as thread deformation or thread serrations. On the other hand, the torque lock nuts have an internal nylon insert that produces friction between the threads and helps keep them from backing off.

ISO 7040 prevailing torque nut Dimensions Table

Hex Nylon Lock Nut-2D

Screw Thread d		M3	M4	M5	M6	M8	M10	M12	(M14)	M16	M20	M24	M30	M36
Screw Thread d		M3	M4	M5	M6	M8	M10	M12	(M14)	M16	M20	M24	M30	M36
P	Pitch	0.5	0.7	0.8	1	1.25	1.5	1.75	2	2	2.5	3	3.5	4
da	max	3.45	4.6	5.75	6.75	8.75	10.8	13	15.1	17.3	21.6	25.9	32.4	38.9
da	min	3	4	5	6	8	10	12	14	16	20	24	30	36
dw	min	4.57	5.88	6.88	8.88	11.63	14.63	16.63	19.64	22.49	27.7	33.25	42.75	51.11
e	min	6.01	7.66	8.79	11.05	14.38	17.77	20.03	23.36	26.75	32.95	39.55	50.85	60.79
h	max	4.5	6	6.8	8	9.5	11.9	14.9	17	19.1	22.8	27.1	32.6	38.9
h	min	4.02	5.52	6.22	7.42	8.92	11.2	14.2	15.9	17.8	20.7	25	30.1	36.4
m	min	2.15	2.9	4.4	4.9	6.44	8.04	10.37	12.1	14.1	16.9	20.2	24.3	29.4
mw	min	1.72	2.32	3.52	3.92	5.15	6.43	8.3	9.68	11.28	13.52	16.16	19.44	23.52
s	max	5.5	7	8	10	13	16	18	21	24	30	36	46	55
s	min	5.32	6.78	7.78	9.78	12.73	15.73	17.73	20.67	23.67	29.16	35	45	53.8
①, Product grade For d ≤ M16:A For d ＞ M16:B ②, Material: Steel, Strength class: d＜M5: subject to the agreement; d≥M5: 5,8,10. Standard: d＜M5: subject to agreement and ISO 2320; d≥M5: ISO898-2 and ISO 2320

Main features or advantages of prevailing torque nut

Prevailing torque nuts have several key characteristics and benefits, including resistance to loosening, ease of installation, corrosion resistance, and long-lasting locking capabilities.

Because of these characteristics, they are a popular choice in various industries, including automotive, aerospace, construction, and manufacturing. Prevailing torque nuts provide a dependable and effective locking solution, whether avoiding vibration-induced loosening or assuring the longevity of an assembly.

news-800-800 — AYA Prevailing Torque Lock Nuts

One of the primary benefits of prevailing torque nuts is their ability to resist loosening under various situations, making them perfect for applications involving vibration or dynamic forces.
One of the most distinguishing characteristics of dominant torque nuts is their distinctive design, which provides excellent resistance to loosening. In contrast to conventional nuts, prevailing torque nuts have a unique locking mechanism that enhances friction between the nut and the mating surface. Even when subjected to external forces such as vibration or shock, the increased friction prevents the nut from rotating freely.
Another benefit of prevailing torque nuts is their simplicity of installation. Unlike other locking systems that need adhesives or additional components, prevailing torque nuts can be installed using conventional tools. This minimizes the overall cost and complexity of the fastening system while simplifying the assembly process.
Prevalent torque nuts are also resistant to corrosion and environmental conditions. They are typically composed of materials resistant to rust and other forms of degradation, such as stainless steel or alloy steel. This makes them suited for use in demanding conditions, such as outdoor applications or industries that frequently expose themselves to wet or chemicals.
Furthermore, torque nuts offer a dependable and long-lasting locking solution. Once properly placed, they retain their locking capabilities for extended periods, maintaining the assembly's integrity and stability. This is especially crucial in critical applications where a fastener failure could have devastating implications.

Engineering Applications Where Prevailing Torque Is Critical

Automotive assemblies (engine, suspension, chassis)
Heavy machinery in high-vibration environments
Aerospace structural joints
Industrial equipment maintenance

In these applications, torque retention ensures longevity, safety, and reduced maintenance.

Practical Engineering Tips

Always specify prevailing torque values in design documents
Use appropriate lock features for vibration-prone environments
Validate torque performance in prototyping and field testing
Pair torque values with preload and tension control

FAQs

Q: What is the prevailing torque in a fastener?

A: Prevailing torque is the additional resistance to rotation created by lock features that helps maintain preload.

Q: Why is prevailing torque important in vibration environments?

A: It helps prevent joint relaxation and loosening under dynamic loads and vibration.

Q: How is prevailing torque measured?

A: Measured using a torque testing device following standard rotational procedures.

Q: Does surface coating affect prevailing torque?

A: Yes, coatings influence friction and torque retention in fastener joints.

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