Overview
ISO 7995:2002 defines the dimensions for hexagonal, self-locking aerospace nuts with MJ threads. The self-locking feature is achieved by forming the upper portion of the nut out-of-round. The standard covers nuts intended for aerospace product standards and specifies classifications based on a minimum ambient tensile stress of 1 100 MPa with maximum service-temperature limits of 235 °C, 315 °C, and 425 °C. All dimensions and tolerances are expressed in millimetres and apply after any surface coatings but before lubrication.
Key topics and requirements
- Scope: Dimensions for hexagonal, self-locking nuts with MJ thread forms; applicable only for compiling aerospace product standards.
- Self-locking method: Achieved by forming the upper portion out-of-round (tooling marks permissible in this zone); tolerances for the self-locking zone apply before forming out-of-round.
- Mechanical-classification: Nuts designed to withstand a minimum tensile stress of 1 100 MPa at ambient temperature and rated for maximum temperatures of 235 °C, 315 °C, or 425 °C (maximum temperature conditioned by sealing ring material or surface treatment).
- Thread range: Covers MJ thread sizes typically from MJ3 to MJ12 (per ISO 5855-2 thread coding and limit dimensions).
- Dimensional details: Figure and table in the standard provide key dimensions (E, F, G, H, K, M, N, Q) and tolerances; values apply after coatings; finished nuts must fit a standard socket wrench.
- Form and position tolerances: Conform to ISO 8788; unspecified form details are at the manufacturer’s discretion.
- Use with procurement specs: Dimensions are chosen to satisfy procurement requirements such as ISO 5858.
Applications and users
ISO 7995 is intended for professionals involved in aerospace fastener systems:
- Aerospace designers and engineers specifying fasteners for airframes and propulsion systems.
- Fastener manufacturers producing hexagonal, self-locking MJ-thread nuts to aerospace tolerances.
- Procurement and quality assurance teams ensuring dimensional conformity for aerospace components.
- Standards compilers and regulatory bodies incorporating nut dimensions into aerospace product standards and procurement documents.
Use cases include high-temperature, high-strength fastening where predictable locking behavior and tight dimensional control are required in aerospace assemblies.
Related standards
- ISO 5855-2 - MJ threads: limit dimensions for bolts and nuts (thread codes and limits referenced by ISO 7995).
- ISO 8788 - Nuts, metric: tolerances of form and position (applies to form/position tolerances used by ISO 7995).
- ISO 5858 - Procurement specification for self-locking nuts with maximum operating temperatures up to 425 °C.
Keywords: ISO 7995, aerospace nuts, hexagonal self-locking nuts, MJ threads, aerospace fasteners, dimensions standard, 1100 MPa, high-temperature nuts.