NF E 25-415 Hex Nuts with Captive Conical Washers

NF E 25-415 Hex Nuts with Captive Conical Washers

Smooth Conical Washer Nut Assemblies | Product Grade A Reference | Custom OEM Manufacturing

Juxin Fasteners manufactures hexagon nuts with captive smooth conical washers for automotive OEMs, industrial machinery manufacturers, equipment suppliers and custom fastening applications.

These nut and washer assemblies combine a hexagonal threaded nut with a separately manufactured washer that is mechanically retained while remaining free to rotate relative to the nut.

The design provides a controlled bearing interface and reduces the need to handle separate washers during installation.

NF E 25-415 is an important French standard reference for hexagon nuts with captive conical washers. The historical 1986 edition has been replaced by the 2022 edition.

Juxin Fasteners also supports customer-engineered variants incorporating metallic prevailing-torque locking features, subject to the approved drawing and functional requirements.

Product Specifications

The listed metric and inch-thread sizes represent the specified product offering, not the complete dimensional scope of NF E 25-415.

Custom versions incorporating metallic locking features must be evaluated separately from the standard nut and washer configuration.

What Is an NF E 25-415 Hex Nut with Captive Washer?

An NF E 25-415 type assembly consists of a hexagonal nut and a smooth conical washer retained as a single handling unit.

The washer is captive, meaning it is not intended to separate during normal handling.

However, the washer may rotate relative to the nut.

This arrangement differs from an integral flange nut because the bearing washer is a separate component.

The assembly can be selected where a controlled bearing surface, conical washer geometry or simplified parts handling is required.

NF E 25-415:1986 and NF E 25-415:2022

NF E 25-415:1986 addressed hexagon nuts with incorporated smooth conical spring washers, product grade A.

The 2022 edition covers hexagon regular nuts with captive smooth conical washers in steel and stainless steel, within its specified metric coarse-thread range of M5–M16.

The applicable edition must be identified on the engineering drawing.

Custom thread sizes, washer geometry or additional locking mechanisms may fall outside the standard configuration.

NF E 25-415 vs. NF E 25-417

These two standards describe different product constructions.

The presence of a captive conical washer does not establish conformity to NF E 25-417.

A metallic locking element must not be described as a nylon or other non-metallic locking insert.

Captive Washer Construction

The washer is mechanically retained to the nut through a drawing-controlled assembly feature.

The design should provide the required retention while allowing specified relative rotation.

Important characteristics include:

• Washer outside diameter.

• Washer inside diameter.

• Washer thickness.

• Cone angle and free height.

• Retention geometry.

• Axial clearance.

• Rotational freedom.

• Bearing surface finish.

• Washer material and hardness.

These parameters affect installation behavior and assembly compatibility.

Smooth Conical Washer Geometry

A smooth conical washer has a defined profile that may provide elastic deflection under loading when properly designed.

Its behavior depends on:

• Washer material.

• Thickness.

• Outside and inside diameters.

• Cone height.

• Hardness.

• Applied load.

• Joint stiffness.

A conical washer must not automatically be assumed to maintain a specified preload or provide vibration resistance without testing.

Why Use a Captive Washer?

A retained washer can simplify handling in manufacturing and assembly operations.

Potential benefits include:

• Reduced handling of loose washers.

• Consistent washer presentation.

• Reduced risk of missing washers.

• Simplified packaging.

• Improved suitability for automated assembly.

• Defined bearing surface geometry.

Actual benefits depend on the product design and assembly equipment.

Captive Washer vs. Integral Flange Nut

The two products should not be substituted without engineering review.

Captive Washer vs. Conventional Keps Nut

A conventional Keps nut generally uses a retained toothed lock washer.

The product described here uses a smooth conical washer.

Its bearing and elastic characteristics are different from those of a toothed washer.

The correct design should be selected according to the joint requirements.

Optional Metallic Prevailing-Torque Locking Feature

Some customer-specific assemblies may incorporate a metallic locking feature in addition to the captive washer.

The locking mechanism may use a spring steel component or a controlled metallic thread-interference feature.

This function must be distinguished from the conical washer's bearing characteristics.

The locking feature creates prevailing torque through resistance to rotation on the mating bolt.

Required functional values must be defined by the customer.

Metric Thread Specifications

These are standard metric coarse-thread references.

The current NF E 25-415 standard covers a defined metric range; M4 and custom configurations must be treated as drawing-specific variants rather than automatically standard-compliant products.

Unified Inch-Thread Specifications

For North American OEM applications, the specified product range includes:

Unified threads should be specified according to ASME B1.1.

These inch-thread products are custom configurations and must not be represented as standard NF E 25-415 dimensions.

Metric and Inch Threads Are Not Interchangeable

Metric and Unified inch threads differ in nominal diameter, pitch and tolerance.

For example, M6×1.0 and 1/4-20 UNC are not interchangeable.

The nut must match the approved mating bolt.

Nut Body Materials

The nut body may be manufactured from customer-specified carbon steel.

The material designation and required mechanical properties must be defined on the engineering drawing.

Material selection should consider:

• Cold forming suitability.

• Thread strength.

• Proof-load requirements.

• Heat treatment.

• Surface treatment.

• Assembly loading.

The supplied material references include M08AL-type cold-heading steel. Chemical composition and mechanical properties must be verified against the approved material specification.

Spring Steel Washer and Locking Components

Spring steel may be selected for the washer or metallic locking component where required.

The supplied material references include 65Mn.

Relevant engineering factors include:

• Elastic behavior.

• Hardness.

• Heat treatment.

• Fatigue resistance.

• Washer deflection.

• Retention geometry.

• Surface protection.

Material properties must be verified for the actual component.

Surface Treatment Options

Juxin Fasteners supports customer-specified surface finishing for custom nut and washer assemblies.

Potential finishes include:

• Zinc plating.

• Zinc-nickel alloy plating.

• Black finishes.

• Electrophoretic coatings where suitable.

• Other drawing-approved surface treatments.

The coating process must be compatible with the nut, washer, locking feature and required relative rotation.

Zinc-Nickel Coating for Automotive Variants

For automotive OEM applications, zinc-nickel alloy plating may be specified.

Customer requirements can include corrosion performance, coating thickness, friction control and appearance.

Where applicable, the coating specification should define:

• Zinc-nickel composition.

• Coating thickness.

• Passivation.

• Sealer or topcoat.

• Friction requirements.

• Salt spray test method.

• Corrosion acceptance criteria.

A specified laboratory salt spray duration must not be interpreted as an equivalent service life.

Coating and Washer Rotation

Surface treatment may affect washer rotation and retention.

The manufacturing process should control:

• Coating buildup.

• Washer clearance.

• Retention deformation.

• Surface friction.

• Corrosion protection.

• Assembly functionality.

Functional checks may be required after finishing.

Washer Retention Testing

A captive washer must remain attached during normal handling and assembly.

Depending on the approved design, relevant tests may include:

• Axial retention force.

• Rotational freedom.

• Washer alignment.

• Retention feature deformation.

• Dimensional inspection.

Acceptance criteria must be established before production.

Torque and Clamp Force Considerations

The tightening torque required for a threaded joint depends on thread friction, bearing friction and the fastener configuration.

For assemblies incorporating a metallic locking feature, prevailing torque must also be considered.

The captive washer may influence the bearing interface, but does not guarantee a particular clamp force.

Testing may be required to establish the relationship between tightening torque and preload.

Automotive OEM Applications

Captive conical washer nut assemblies may be used in suitable automotive fastening applications.

Potential applications include:

• Vehicle mounting brackets.

• Fabricated steel components.

• Equipment support assemblies.

• Body and underbody hardware.

• Customer-engineered fastening interfaces.

The product must satisfy the approved OEM mechanical, corrosion and assembly requirements.

Industrial Machinery

Industrial machinery manufacturers may use captive washer nut assemblies where washer handling, bearing geometry and installation consistency are important.

Applications may include:

• Machine mounting brackets.

• Equipment housings.

• Mechanical support assemblies.

• Industrial covers.

• Fabricated steel components.

Electrical Equipment and Enclosures

Electrical equipment manufacturers may require nut and washer assemblies for mounting structures and cabinet hardware.

Selection should consider:

• Bearing surface.

• Panel material.

• Electrical continuity where required.

• Corrosion protection.

• Assembly accessibility.

Transportation and Rail Equipment

Transportation equipment may require captive washer nut assemblies with defined mechanical properties and retention performance.

Vibration, fatigue, corrosion and safety requirements must be established by the relevant project specification.

Agricultural and Construction Machinery

Captive washer nut assemblies may be evaluated for suitable equipment brackets and fastening interfaces.

The design must account for mechanical loading, environmental exposure and service requirements.

Why Sealing Performance Is Not Assumed

A smooth conical metal washer is not automatically a sealing washer.

The product should not be used as a hydraulic or pneumatic sealing component without an approved sealing design and validated leakage performance.

If sealing is required, the customer must specify the sealing material, geometry and test criteria.

Cold Heading and Nut Manufacturing

Juxin Fasteners supports cold heading and cold forming for suitable nut designs.

Manufacturing process selection depends on:

• Material grade.

• Nut geometry.

• Thread dimensions.

• Production volume.

• Mechanical properties.

• Dimensional tolerances.

Washer Forming and Mechanical Assembly

The washer may be manufactured through suitable forming processes and subsequently assembled to the nut.

Important manufacturing controls include:

• Washer dimensions.

• Cone geometry.

• Material hardness.

• Retention feature dimensions.

• Assembly deformation.

• Washer movement.

• Final dimensional consistency.

CNC Machining and Secondary Operations

CNC machining may be used where customer-specific geometry or tolerances require it.

Secondary processes may include threading, heat treatment, surface finishing and inspection.

The manufacturing route is selected according to the approved drawing.

Custom OEM/ODM Manufacturing

Juxin Fasteners supports made-to-drawing manufacturing for custom captive washer nut assemblies.

Customization may include:

• Metric threads.

• Unified UNC/UNF threads.

• Nut dimensions.

• Washer outside diameter.

• Washer thickness.

• Washer cone angle.

• Retention geometry.

• Washer rotational clearance.

• Material grades.

• Mechanical properties.

• Optional metallic locking feature.

• Surface coating.

• Inspection requirements.

• Packaging.

Custom designs are subject to engineering feasibility review.

Quality Inspection

Depending on the customer specification, inspection may include:

• Material verification.

• Thread gauging.

• Nut dimensions.

• Washer dimensions.

• Washer hardness.

• Washer retention.

• Rotational freedom.

• Mechanical properties.

• Prevailing torque where applicable.

• Coating thickness.

• Corrosion testing where specified.

• Packaging inspection.

The inspection plan must follow the approved customer requirements.

Production Manager Considerations

Production managers should evaluate:

• Nut and washer feeding orientation.

• Washer retention consistency.

• Rotational freedom.

• Assembly cycle time.

• Coating compatibility.

• Installation torque.

• Inspection requirements.

• Batch consistency.

• Packaging and delivery scheduling.

Purchasing and Supplier Development

Purchasing managers and supplier development engineers should provide:

• Approved engineering drawing.

• NF E 25-415 edition where applicable.

• Nut and washer materials.

• Thread designation.

• Nut dimensions.

• Washer profile and dimensions.

• Retention geometry.

• Washer rotational requirements.

• Optional locking feature requirements.

• Surface treatment.

• Mechanical properties.

• Initial order quantity.

• Estimated annual demand.

Relevant International Standards

The following references may be relevant depending on the approved design:

• NF E 25-415:1986: Historical hexagon nut and conical washer standard.

• NF E 25-415:2022: Current hexagon nut and captive conical washer standard.

• NF E 25-417:2021: Separate standard for non-metallic insert prevailing-torque hex nuts with captive conical washers.

• ISO 2320: Functional properties of applicable prevailing-torque steel nuts.

• ISO 898-2: Mechanical properties of applicable carbon steel and alloy steel nuts.

• ISO 261: ISO metric screw-thread general plan.

• ISO 965 Series: ISO metric screw-thread tolerances.

• ASME B1.1: Unified inch screw threads.

• ISO 16047: Torque–clamp force testing within the applicable scope.

• ISO 9227: Salt spray corrosion testing.

Reference to these standards does not independently establish product conformity.

The approved engineering drawing remains controlling.

Frequently Asked Questions

What is an NF E 25-415 captive washer nut?

It is a hexagon nut assembly with a retained smooth conical washer, as defined within the applicable standard configuration.

Is the washer free to rotate?

The supplied product design uses a mechanically retained washer that can rotate relative to the nut.

Is NF E 25-415:1986 still current?

No. It has been replaced by NF E 25-415:2022.

What is the difference between NF E 25-415 and NF E 25-417?

NF E 25-415 addresses captive conical washer nut assemblies. NF E 25-417 addresses prevailing-torque hexagon nuts with non-metallic locking inserts and captive conical washers.

Does every NF E 25-415 nut have a self-locking thread?

No. A metallic or non-metallic prevailing-torque feature must be specified separately where required.

Can a custom metallic locking feature be added?

Yes. Customer-specific locking configurations can be evaluated according to the approved drawing.

What metric sizes are included in the supplied range?

M4, M5, M6, M8, M10 and M12.

What inch-thread sizes are included?

#8-32, #10-32, 1/4-20, 5/16-18, 3/8-16 and 1/2-13.

Are metric and inch threads interchangeable?

No. The exact thread designation must match the mating bolt.

Does the washer provide sealing?

No sealing performance is claimed without a specific design and validation.

Can Juxin Fasteners manufacture custom washer dimensions?

Yes. Washer geometry, material and retention requirements can be evaluated according to customer drawings.

Can these assemblies be used in automotive manufacturing?

Yes, where the approved design and functional requirements support the application.

Request a Quote — Captive Conical Washer Hex Nuts

Juxin Fasteners manufactures custom industrial fasteners for automotive OEMs, Tier-1 and Tier-2 suppliers, machinery manufacturers, mechanical engineers, 

manufacturing engineers, production managers, purchasing managers and supplier development teams.

Our manufacturing capabilities include cold heading, cold forming, CNC machining where required, washer forming, mechanical assembly and suitable secondary operations.

We support OEM/ODM manufacturing, made-to-drawing fasteners and industrial batch production.

Recommended RFQ Information

• 2D engineering drawing or 3D CAD model.

• Applicable NF E 25-415 edition.

• Metric or Unified thread designation.

• Nut material and mechanical properties.

• Washer material and hardness.

• Washer outside diameter and thickness.

• Washer cone angle and free height.

• Retention geometry.

• Washer rotational clearance.

• Optional locking mechanism.

• Prevailing torque requirements where applicable.

• Surface treatment.

• Inspection requirements.

• Initial order quantity.

• Estimated annual demand.

• Packaging and delivery requirements.

Please send your engineering drawings and technical specifications for manufacturing feasibility review and quotation.

Juxin Fasteners

Industrial Fastener Manufacturer | NF E 25-415 Captive Conical Washer Nuts | Custom Hex Nut and Washer Assemblies | OEM/ODM Manufacturing

Website: https://www.juxinfasteners.com/

Email: 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.