ISO 8168:2025

Overview

ISO 8168:2025 - "Aerospace - Bolts, with MJ threads, made of heat and corrosion resisting steel, strength class 1 100 MPa - Procurement specification" is an International Standard that defines the characteristics, manufacturing and quality assurance requirements for MJ-thread bolts used in aerospace construction. It is a procurement specification intended to be applied whenever referenced in a definition document (e.g., drawing or contract). The standard targets bolts made of heat- and corrosion-resisting steel with a strength class of 1 100 MPa and replaces the previous (2016) edition with updated sampling, dimensional and mechanical test requirements.

Key Topics and Requirements

• Material and strength class: Bolts must be of heat- and corrosion-resisting steel meeting requirements defined in the applicable definition document and strength class 1 100 MPa.
• Manufacturing controls: Requirements for forging, heat treatment, thread forming (threads rolled after full heat treatment), surface condition, and permissible surface coatings. Heads must be formed by hot or cold forging and blanks shall not be heat-treated more than twice.
• Quality assurance: Manufacturers must be capable of continuous compliant production and are encouraged to operate a recognized quality management system. Quality records must be retained for at least 10 years.
• Inspection and sampling:
  • Qualification inspection: Typically performed on each bolt type/diameter; e.g., 25 bolts selected from a single inspection lot by simple random sampling.
  • Production acceptance: Sampling plans follow AS/EN 9138 and the sampling tables in ISO 8168. Acceptance inspections include visual, dimensional and mechanical tests.
• Mechanical tests: Tensile strength and double-shear strength tests are specified (ISO 7961 test methods). The standard lists exceptions for short or special bolts where tensile/double-shear tests do not apply.
• Non-destructive testing: References include ISO 3452-1 (penetrant testing) for detecting surface-breaking defects.
• Statistical Process Control (SPC): SPC may be substituted for final sampling if validated, documented and approved by the qualifying body (not applicable to destructive tests).
• Annexes: Informative annexes provide cross-sectional area and load formulae for tensile and double-shear calculations.

Applications and Who Uses It

ISO 8168:2025 is used by:

• Aerospace fastener manufacturers and heat-treatment shops to define production and test methods for MJ-thread bolts.
• Procurement and supply chain engineers specifying bolts for aircraft and space vehicle assemblies.
• Quality managers, inspectors and auditors implementing acceptance criteria and sampling plans.
• Design and stress engineers requiring consistent mechanical property and sizing data for bolted joints.

Keywords: ISO 8168:2025, MJ threads, aerospace bolts, heat and corrosion resisting steel, strength class 1100 MPa, procurement specification, quality assurance, sampling, tensile strength, double shear, SPC.

Related standards

• ISO 5855-2 (MJ threads - limit dimensions)
• ISO 7961 (Bolts - test methods)
• ISO 3452-1 (Penetrant testing)
• AS/EN 9138 (Statistical product acceptance)
• ASTM E112 (Grain size determination)