Overview
The EN ISO 10484:2004 standard, titled Widening Test on Nuts (ISO 10484:1997), establishes a uniform procedure for testing the structural integrity and surface acceptability of mechanical nuts. Developed by the International Organization for Standardization (ISO) and adopted as a European Standard by CEN, this document supersedes the previous EN 493:1992 standard. It applies specifically to nuts with property classes defined in ISO 898-2 and ISO 898-6, covering nominal thread diameters from 5 mm to 39 mm, and product grades A and B.
This standard is critical for manufacturers, quality control professionals, and engineers to ensure reliability and performance of nuts in various mechanical assemblies.
Key Topics
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Test Scope: Applies to nuts excluding those made from free cutting steel, ensuring that nuts meet surface discontinuity criteria specified in ISO 6157-2.
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Test Principle: The widening test involves removing threading to the nominal diameter, then pushing a tapered mandrel through the nut hole. The widening of the nut hole, expressed as a percentage of the hole diameter, is measured to determine acceptability.
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Mandrel Specifications: The tapered mandrel must be polished, have a hardness of at least 45 HRC, and meet precise dimensional tolerances. Two mandrel sizes correspond to widening measurements of either 4% or 6%.
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Test Procedure: Lubricate the mandrel with molybdenum disulphide (MoS₂) for smooth insertion, then insert it slowly (maximum 25 mm/min) under axial load until it reaches the cylindrical part of the hole.
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Acceptance Criteria:
- Nuts with property classes 4 to 12 require a minimum 6% widening.
- Property classes 04 and 05 require a minimum 4% widening.
- Prevailing torque type nuts (per ISO 2320) have a reduced widening requirement, 20% less than hexagon nuts.
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Failure Identification: Premature fracture or complete wall breakage before meeting widening percentages constitutes failure. Verification can include cutting the nut to confirm fracture location.
Applications
The EN ISO 10484:2004 widening test standard is essential for:
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Quality Control in Fastener Manufacturing
Ensuring nuts meet mechanical and surface quality standards to prevent failures in critical applications.
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Mechanical Engineering Design
Selecting nuts with verified mechanical properties suited for load-bearing, fastening, and vibration-resistant assemblies.
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Automotive and Aerospace Industries
Where safety-critical fasteners require rigorous testing to meet performance and durability standards.
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Standardized Product Certification
Enabling manufacturers to certify and label nuts compliant with European and international fastener quality requirements.
Related Standards
- ISO 898-2 – Mechanical properties of fasteners: Nuts with specified proof load values (Coarse thread).
- ISO 898-6 – Mechanical properties of fasteners: Nuts with specified proof load values (Fine pitch thread).
- ISO 6157-2 – Surface discontinuities: Requirements for nuts.
- ISO 2320 – Prevailing torque type steel hexagon nuts: Mechanical and performance requirements.
By implementing the EN ISO 10484:2004 standard, organizations ensure that nuts used in engineering applications comply with internationally recognized safety and performance benchmarks. This standard supports product reliability and contributes to the overall integrity of mechanical fastening solutions.