EN 20898-7:1995

Overview

The EN 20898-7:1995 standard, titled Mechanical properties of fasteners - Part 7: Torsional test and minimum torques for bolts and screws with nominal diameters 1 mm to 10 mm (ISO 898-7:1992), establishes critical testing methods and mechanical requirements for fasteners. Issued by the European Committee for Standardization (CEN), this standard focuses on specific classes of bolts and screws-property classes 8.8 to 12.9 as per ISO 898-1-covering fasteners with nominal thread diameters from 1 mm to 10 mm.

This part is essential where conventional tensile testing is unsuitable, including for fasteners with thread diameters smaller than M3 or short bolts and screws between 3 mm and 10 mm that cannot undergo tensile stress tests. It provides key insights into torsional testing methods and the minimum torque values to ensure safety, reliability, and performance of small-diameter fasteners used in critical mechanical assemblies.

Key Topics

• Scope of Fasteners Covered
  Applies primarily to bolts and screws of property classes 8.8 to 12.9 as defined in ISO 898-1

  • Bolts and screws with thread diameters less than M3 lacking indicated breaking and proof loads in ISO 898-1
  • Short bolts and screws with nominal diameters from 3 mm to 10 mm unsuitable for tensile testing
  • Excludes hexagon socket set screws for minimum breaking torque applicability

• Torsional Testing Methodology
  Details the standardized procedure for conducting torsional tests to measure torsional strength and mechanical behavior under twisting loads
  Ensures consistency in determining mechanical reliability of small fasteners subjected to torque in actual applications

• Minimum Torque Requirements
  Specifies minimum breaking torques essential for quality assurance and performance benchmarking
  Supports design engineers and quality control experts in selecting bolts and screws capable of withstanding operational stresses

• Compliance with ISO 898-7:1992
  Harmonizes European standards with international benchmarks, facilitating global manufacturing and testing practices for fasteners

Applications

This standard is extensively utilized in industries where small-diameter bolts and screws are critical for mechanical integrity and safety, such as:

• Mechanical Engineering and Assembly
  Ensures reliable torque specifications for miniature fasteners in machinery and equipment
• Automotive and Aerospace Industries
  Integral for components requiring precise torque control and mechanical performance under dynamic loads
• Electronics and Electrical Devices
  Provides specifications for tiny fasteners used in delicate assemblies where tensile testing may be impractical
• Quality Assurance Laboratories and Testing Facilities
  Standardizes torsional testing procedures to maintain fastener performance compliance and certification

By adhering to EN 20898-7:1995, manufacturers and engineers can guarantee that fasteners meet minimum strength requirements, reducing failure risk and improving product longevity.

Related Standards

• ISO 898-1 - Mechanical properties of fasteners - Part 1: Bolts, screws, and studs with specified property classes
• ISO 898-7:1992 - International equivalent detailing torsional test and torque requirements for small fasteners
• EN 20898-1 series - Covers tensile testing and mechanical properties of fasteners with larger nominal diameters
• CEN EN 20898 series - Comprehensive standards covering a wide range of fastener mechanical properties and testing protocols

These related standards complement EN 20898-7:1995 by addressing different fastener sizes, material classes, and mechanical testing methods, enabling holistic fastener quality control.

Keywords: EN 20898-7, torsional test, minimum torque, bolts, screws, fasteners, ISO 898-7, mechanical properties, small-diameter fasteners, property classes 8.8 to 12.9, tensile test alternative, CEN standards, fastener testing, torque specifications.