All-Metal Prevailing-Torque Lock Nuts for High-Vibration Industrial Assemblies

Industrial compressors, railway equipment, pumps, motors, HVAC systems, construction machinery and other dynamic equipment can expose bolted joints to vibration,

 temperature changes, repeated loading and maintenance cycles.

In these applications, engineers frequently search for a “vibration-proof nut.”

That description is convenient, but technically misleading.

No lock nut should be treated as a substitute for a correctly designed bolted joint.

Joint preload, bolt stiffness, clamped-part stiffness, tightening method, bearing surfaces, transverse movement, 

temperature, lubrication and service loading all influence whether a bolted joint remains secure.

An all-metal prevailing-torque lock nut adds resistance to relative rotation through a mechanical locking feature within the nut.

Unlike a nylon-insert lock nut, the locking function does not depend on a polymer insert.

JUXIN FASTENERS supplies and develops multiple locking nut families, including:

• All-metal prevailing-torque lock nuts

• Stover-type lock nuts

• Distorted-thread lock nuts

• All-metal flange lock nuts

• Fuji-style all-metal flange lock nuts

• Spring-stop style locking nuts

• Stainless steel all-metal lock nuts

• Drawing-based custom locking nuts

These products can be evaluated for compressors, railway equipment, motors, pumps, industrial machinery, automotive equipment, 

HVAC systems and other applications where a polymer locking element may not be the preferred solution.

What Is an All-Metal Prevailing-Torque Lock Nut?

An all-metal prevailing-torque nut uses controlled metallic thread interference or another mechanical deformation feature to create resistance as the nut travels along the mating bolt thread.

This resistance exists independently of the final clamping load.

That resistance is called prevailing torque.

Depending on nut design, the locking feature may involve:

• Controlled deformation of the upper thread region

• Distorted thread geometry

• Deformed nut sections

• Multiple locking segments

• Spring-type metallic locking features

• Application-specific all-metal locking geometry

The exact mechanism varies by product family.

The important engineering distinction is that prevailing torque is not the same as tightening torque and is not the same as clamp load.

Prevailing Torque, Tightening Torque and Clamp Load Are Different

This distinction is essential when specifying a lock nut.

Prevailing Torque

Prevailing torque is the torque required to rotate the nut on the mating thread when the nut's locking feature is engaged but before the joint is fully clamped.

Tightening Torque

Tightening torque is the torque applied during final assembly.

It must overcome several sources of resistance, including thread friction, under-head or bearing-surface friction and, for a prevailing-torque nut, the locking feature itself.

Clamp Load

Clamp load is the tension generated in the bolt and the corresponding compression in the clamped components.

A lock nut can have significant prevailing torque while the assembled joint still has insufficient preload.

This is why specifying only “high locking torque” does not guarantee a reliable bolted joint.

Why All-Metal Lock Nuts Are Used in Dynamic Equipment

All-metal locking nuts are often considered where the application includes:

• Vibration

• Repeated dynamic loading

• Elevated service temperature

• Exposure conditions unsuitable for a polymer insert

• Industrial fluids or chemicals

• Compact joint geometry

• OEM requirements for an all-metal locking mechanism

Typical industries include:

• Industrial compressors

• Railway equipment

• Motors and generators

• Pumps

• HVAC equipment

• Industrial machinery

• Construction equipment

• Agricultural machinery

• Automotive systems

• Material-handling equipment

• Power equipment

• Automation systems

The correct nut still needs to be selected according to the bolt, joint and service environment.

All-Metal Lock Nut vs Nylon-Insert Lock Nut

Both are prevailing-torque locking technologies, but their locking mechanisms are different.

Neither technology is universally superior.

A DIN 985-type nylon insert lock nut can be an effective and economical solution in many applications.

An all-metal nut becomes particularly relevant when the service environment or engineering specification makes a polymer insert undesirable.

Information Gain: A Lock Nut Does Not “Absorb Vibration”

All-metal lock nuts are sometimes described as absorbing vibration.

That is not an accurate description of the primary locking mechanism.

The nut does not function like a vibration isolator or damping mount.

Instead, the locking feature creates resistance to relative rotation between the nut and mating thread.

The distinction matters because the actual bolted joint may still experience:

• Transverse slip

• Embedment

• Settlement

• Thermal expansion

• Joint separation

• Fatigue loading

The lock nut is one element in the joint.

It does not eliminate the underlying mechanical loads.

Why Bolted Joints Loosen Under Transverse Movement

One of the most challenging conditions for threaded joints is transverse movement between the clamped parts.

If relative movement becomes sufficient to reduce frictional restraint at the thread and bearing interfaces, rotational loosening can occur.

The probability of loosening depends on the complete joint, including:

• Initial preload

• Joint stiffness

• Bolt stiffness

• Bearing surface

• Friction condition

• Transverse displacement

• External loading

• Thread geometry

• Locking mechanism

This explains why simply replacing a standard nut with a lock nut may improve the joint but does not automatically correct an underlying preload or joint-design problem.

Railway Assemblies: Vibration Is Only Part of the Problem

Rail equipment is frequently described as a “high-vibration application,” but that description is incomplete.

A railway bolted joint can also experience:

• Repeated mechanical loading

• Shock

• Temperature variation

• Environmental exposure

• Maintenance cycles

• Corrosion

• Joint movement

Fastener selection should therefore be based on the actual assembly location and engineering requirement.

Potential applications for locking nuts may include:

• Equipment mounting

• Interior equipment structures

• Electrical equipment

• HVAC assemblies

• Brackets

• Auxiliary systems

• Machinery installed on rolling stock

Safety-critical railway joints require application-specific engineering specifications, validation and approvals.

A general-purpose lock nut should never be assumed suitable for a safety-critical rail location merely because it is all-metal.

Compressor Assemblies: Consider Temperature, Oil and Cyclic Loading Together

Industrial compressors can combine several demanding conditions:

• Mechanical vibration

• Cyclic loading

• Elevated temperature

• Lubricating oils

• Maintenance access

• Rotating or reciprocating machinery

A nylon-insert nut may or may not be appropriate depending on the actual temperature and chemical environment.

All-metal prevailing-torque nuts remove the polymer insert from the locking mechanism, but this does not mean every all-metal nut is automatically suitable for every compressor location.

Engineers should define:

• Service temperature

• Bolt material

• Nut material

• Lubrication condition

• Required property class

• Surface treatment

• Tightening method

• Maintenance requirement

before finalizing the fastener.

High Temperature: Avoid One Universal Temperature Rating

It is tempting to advertise an all-metal lock nut as a “300°C lock nut.”

That can be misleading without defining the complete fastener system.

Temperature capability can depend on:

• Nut material

• Bolt material

• Strength class

• Surface treatment

• Lubricant

• Coating

• Required mechanical properties

• Exposure duration

Removing the nylon insert eliminates one polymer-related temperature constraint.

It does not create one universal operating temperature for every all-metal lock nut.

For high-temperature applications, the service condition should be included in the RFQ.

All-Metal Lock Nuts for Motors and Pumps

Electric motors, pumps and related rotating equipment can create vibration and cyclic loading at:

• Mounting points

• Brackets

• Covers

• Auxiliary components

• Equipment frames

All-metal lock nuts can be evaluated where the joint design requires a prevailing-torque nut and a polymer insert is not preferred.

The correct solution depends on:

• Bolt size

• Property class

• Joint load

• Temperature

• Corrosion environment

• Maintenance cycle

• Required locking characteristics

All-Metal Lock Nuts for HVAC Equipment

HVAC systems can contain:

• Compressors

• Fans

• Motors

• Pumps

• Structural frames

• Sheet-metal equipment

• Outdoor equipment

This creates several different fastening environments within one system.

The same lock nut should not automatically be specified for every location.

For example, an internal motor bracket and an outdoor structural mounting point can have very different corrosion and mechanical requirements.

Fastener standardization should therefore be balanced against actual application conditions.

Stover-Type All-Metal Lock Nuts

Stover-style lock nuts are a widely recognized form of all-metal prevailing-torque nut.

The upper portion of the nut is mechanically deformed to create interference with the mating bolt thread.

Potential applications include:

• Industrial machinery

• Compressors

• Equipment frames

• Motors

• Pumps

• Construction machinery

• Agricultural machinery

• Dynamic mechanical assemblies

Depending on the required geometry and specification, standards such as ISO 7042 and related prevailing-torque nut standards may be relevant.

The applicable standard should be confirmed from the customer drawing or specification rather than assumed from appearance alone.

DIN 980 and Related All-Metal Lock Nut Designs

DIN 980 is commonly associated with prevailing-torque all-metal hexagon nuts.

However, products described commercially as “DIN 980 lock nuts” can still require careful specification.

Procurement teams should confirm:

• Thread

• Nut style

• Mechanical property requirement

• Dimensions

• Locking configuration

• Surface finish

• Applicable current specification or customer drawing

A product name alone is not enough for controlled OEM sourcing.

All-Metal Flange Lock Nuts

An all-metal flange lock nut combines a prevailing-torque locking mechanism with an integrated flange.

Depending on the design, the flange can provide a larger bearing area than a conventional hex nut.

Potential applications include:

• Machinery frames

• Motor mounts

• Equipment brackets

• Automotive components

• Construction equipment

• Industrial assemblies

The flange does not automatically eliminate the need for engineering review of the bearing surface.

Joint material, hole geometry, surface pressure and required washer function should still be considered.

Fuji-Style All-Metal Flange Lock Nuts

Some applications use all-metal flange lock nuts with spring-like locking features rather than a conventional distorted-top geometry.

JUXIN FASTENERS supports Fuji-style all-metal flange lock nuts, including drawing-specific configurations for OEM applications.

These products can be relevant where engineers require:

• All-metal construction

• Integrated flange

• Prevailing-torque locking

• Compact assembly

• Application-specific locking geometry

The locking feature should be evaluated according to the mating bolt, thread and required prevailing-torque behavior.

For non-standard configurations, a drawing is strongly recommended.

Information Gain: Same Thread Size Does Not Mean Same Lock Nut

Two M8 all-metal lock nuts can look similar while having different functional characteristics.

Differences may include:

• Nut height

• Width across flats

• Flange geometry

• Thread tolerance

• Locking deformation

• Prevailing-torque range

• Material

• Property class

• Coating

• Lubrication

• Bearing surface

This is particularly important when replacing an existing OEM component.

A dimensional substitute may fit the bolt but still behave differently during automated tightening or final service.

ISO 2320 and Prevailing-Torque Performance

ISO 2320 provides functional requirements related to prevailing-torque steel nuts.

For applications specified to an applicable prevailing-torque standard, engineers and procurement teams should consider characteristics such as:

• First installation prevailing torque

• Removal prevailing torque

• Subsequent installation/removal behavior where applicable

• Proof load requirements

• Mating fastener conditions

The exact requirements depend on the nut type, size, property class and applicable specification.

JUXIN FASTENERS should evaluate the requested standard and test requirement at RFQ stage rather than assuming every all-metal lock nut uses the same acceptance criteria.

What the Junker Test Actually Tells You

Transverse vibration testing is widely used to evaluate self-loosening behavior of bolted joints.

The commonly referenced Junker test subjects a bolted joint to transverse displacement while monitoring changes in clamp load.

This type of test can be useful for comparing locking strategies under controlled conditions.

However:

Passing a vibration test does not prove that a fastener is universally vibration-proof.

Test results depend on:

• Test configuration

• Joint geometry

• Preload

• Fastener size

• Surface condition

• Transverse displacement

• Test procedure

If a customer requires vibration validation according to a specified test method, the requirement should be defined before production.

JUXIN FASTENERS does not treat a generic “Junker tested” statement as a substitute for the customer's actual application requirement.

Reusability: Do Not Assume Unlimited Installation Cycles

All-metal prevailing-torque nuts are sometimes marketed as indefinitely reusable.

That is not a safe engineering assumption.

Each installation and removal cycle can affect:

• Locking geometry

• Thread surfaces

• Coating

• Lubrication

• Prevailing torque

• Mating bolt condition

If reuse is required, engineers should define the permitted number of cycles and the minimum acceptable prevailing torque according to the applicable specification or internal validation.

For maintenance-critical applications, replacement after removal may still be the preferred policy.

Stainless Steel All-Metal Lock Nuts and Galling

Stainless steel threaded assemblies require special attention to galling.

Galling is adhesive wear that can occur when mating stainless threads slide under load.

Risk can be influenced by:

• Material combination

• Surface finish

• Lubrication

• Tightening speed

• Thread fit

• Installation load

A prevailing-torque feature creates additional thread interaction, making assembly conditions particularly important.

For stainless steel lock nut applications, engineers should consider the complete nut-bolt pairing and assembly process rather than specifying “A2 stainless” alone.

A2-70 All-Metal Lock Nuts

JUXIN FASTENERS supports stainless steel locking nut applications, including A2-70 all-metal lock nut configurations where appropriate to the product and drawing.

For OEM sourcing, specify:

• Thread size

• Nut geometry

• Material/property requirement

• Locking style

• Flange requirement

• Surface condition

• Mating bolt specification

• Required functional testing

This is particularly important for small all-metal flange lock nuts where the external appearance may not identify the locking mechanism.

Surface Treatment and Friction Control

Surface finish is not purely a corrosion decision.

It can also influence friction during tightening.

Possible requirements for carbon-steel lock nuts may include:

• Zinc plating

• Zinc-nickel plating

• Customer-specified coating systems

• Lubricated finishes

The appropriate finish depends on:

• Corrosion environment

• Tightening process

• Required friction behavior

• Mating bolt coating

• Customer specification

A change in coating or lubrication can change torque-tension behavior even if the nut dimensions remain unchanged.

This is why procurement teams should not approve a finish substitution based only on appearance or salt-spray hours.

Information Gain: Prevailing Torque Changes the Assembly Torque Budget

When tightening a conventional nut, much of the applied torque is already consumed by friction.

With a prevailing-torque nut, an additional portion of the tool output is required to overcome the locking feature.

Therefore:

Tool torque should not automatically be interpreted as bolt preload.

If an automated assembly process uses torque control, engineers should understand how prevailing torque interacts with the tightening strategy.

This becomes especially important when:

• Prevailing torque is relatively high

• Bolt size is small

• Clamp load is tightly controlled

• Automated nutrunners are used

• Coating or lubrication changes

For critical joints, tightening strategy should be validated on the actual fastener combination.

Property Class and Nut Strength

For carbon-steel nuts, mechanical property requirements may be specified according to standards such as ISO 898-2, where applicable.

The required nut property class should match the joint design and mating bolt requirements.

Higher property class is not automatically better.

Using an unnecessarily high-strength nut can:

• Increase cost

• Change manufacturing requirements

• Provide no functional benefit if the bolt or joint does not require it

The fastener system should be specified according to the actual mechanical design.

Engineering Search Path: How to Select an All-Metal Lock Nut

Design engineers should begin with these questions:

Why is a locking nut required?

Vibration, temperature, service policy or OEM specification?

Is a polymer insert acceptable?

If yes, a nylon-insert lock nut may remain a valid option.

What is the bolt specification?

Thread, property class, material and coating matter.

What prevailing-torque behavior is required?

Define the applicable standard or customer requirement.

What is the operating temperature?

Evaluate the complete material and coating system.

Will the nut be removed during maintenance?

Define reuse policy if applicable.

Is corrosion resistance required?

Select material and finish according to the actual environment.

Is assembly automated?

Prevailing torque and friction can influence tightening strategy.

This decision path is more useful than searching for a generic “anti-vibration nut.”

Procurement Search Path: What to Include in an All-Metal Lock Nut RFQ

For accurate quotation and technical evaluation, provide:

• Thread size and pitch

• Standard or customer drawing

• Lock nut style

• Nut dimensions

• Flange requirement

• Material

• Property class where applicable

• Stainless grade where applicable

• Surface finish

• Mating bolt specification

• Operating temperature

• Application environment

• Required prevailing-torque test

• Reuse requirement if applicable

• Vibration test requirement if applicable

• Prototype quantity

• Annual quantity

• Packaging requirements

• Inspection requirements

For replacement projects, sending the existing drawing is much safer than requesting only an “equivalent Stover nut.”

What Procurement Teams Should Compare Between Suppliers

For prevailing-torque lock nuts, compare more than dimensional fit and unit price.

Important factors include:

• Material

• Mechanical property requirement

• Thread quality

• Locking geometry

• Prevailing-torque consistency

• Surface treatment

• Lubrication condition

• Dimensional consistency

• Sample approval

• Test requirements

• Drawing revision control

• Packaging

• Production repeatability

A nut that looks identical can behave differently during tightening if the locking geometry, coating or lubrication changes.

Custom All-Metal Lock Nuts for OEM Applications

Standard ISO and DIN prevailing-torque nuts cover many industrial requirements.

Custom designs may be needed where the OEM requires:

• Special flange geometry

• Restricted nut height

• Special locking feature

• Non-standard thread

• Stainless steel construction

• Small-size locking nut

• Special bearing surface

• Drawing-specific dimensions

JUXIN FASTENERS supports drawing-based custom locking nut projects in addition to standard locking nut families.

For custom projects, the mating bolt and functional requirement should be supplied together with the nut drawing.

From Joint Requirement to Production

A practical development path for an OEM lock nut project can follow:

Joint Requirement → Locking Method Selection → Drawing & Mating Bolt Review → Material & Finish Confirmation 

→ Sample Evaluation → Prevailing-Torque / Assembly Validation → Golden Sample Approval → Production

The required tests should be agreed according to the customer specification and application rather than assumed from the product category.

JUXIN FASTENERS supports OEM manufacturers, equipment builders, Tier suppliers, industrial distributors and supplier-development teams with standard and drawing-based locking nut solutions.

Related JUXIN FASTENERS Locking Solutions

This page serves as an engineering entry point for all-metal prevailing-torque lock nuts.

Related product and solution pages can include:

• Stover All-Metal Lock Nuts — distorted-thread prevailing-torque nuts for industrial applications

• DIN 980 All-Metal Lock Nuts — standard-based all-metal locking nut configurations

• All-Metal Flange Lock Nuts — integrated flange and metallic prevailing-torque locking

• Fuji-Style All-Metal Flange Lock Nuts — spring-stop style locking configurations

• A2-70 Stainless Steel All-Metal Lock Nuts — stainless locking solutions for selected OEM applications

• DIN 985 Nylon Insert Lock Nuts — polymer-insert prevailing-torque nuts for suitable environments

• Custom Lock Nuts — drawing-based locking geometry and non-standard configurations

• Precision Locknuts for CNC Spindles and Rotary Systems — precision bearing-retention nuts, which solve a different engineering problem from prevailing-torque lock nuts

These pages should target their own specific product intent and link back to this engineering guide where appropriate.

Send Us Your All-Metal Lock Nut Application

If you are designing or sourcing locking nuts for:

• Industrial compressors

• Railway equipment

• Motors

• Pumps

• HVAC systems

• Industrial machinery

• Construction equipment

• Agricultural machinery

• Automotive assemblies

• Power equipment

• Automation systems

• Dynamic mechanical equipment

send us your drawing, thread specification, mating bolt information, material requirement, surface finish, 

service temperature, locking requirement and estimated quantity.

If the project includes a specific prevailing-torque, vibration or reuse requirement, include the applicable test specification or acceptance criteria with the RFQ.

JUXIN FASTENERS can evaluate Stover-type all-metal lock nuts, all-metal flange lock nuts, Fuji-style locking nuts, 

stainless steel lock nuts and drawing-based custom locking nut configurations according to the application.

JUXIN FASTENERS

Website: www.juxinfasteners.com

Engineering & RFQ: info@juxinfasteners.com

Packaging Standard

At Juxin Fasteners, we apply standardized export packaging to ensure product protection, traceability, and compliance with international logistics requirements.

1. Standard Export Packaging

Unless otherwise specified, all products will be packed according to our factory standard export packaging, which includes:

Moisture-resistant inner protection

Poly bag or small box packing as required

Reinforced export cartons

Clear labeling with part number, specification, batch number, and quantity

Palletizing for sea or air shipment when necessary

Our standard packaging is designed to ensure safe transportation, efficient warehousing, and long-distance international shipping.

2. Customized Packaging Options

We also provide customized packaging solutions according to customer requirements, including but not limited to:

Private labeling

Customized barcodes

Specific carton dimensions

Retail packaging

Special pallet configuration

Customer-specific marking and identification

So that you know, customized packaging may involve additional costs and extended lead time depending on the complexity of the requirements.

3. Compliance & Quality Assurance

All packaging processes are controlled under our ISO 9001 quality management system to ensure consistency, traceability, and product integrity throughout the supply chain.