Overview
ISO 12268:1997 - Aerospace - Nuts, hexagonal, plain, reduced height, reduced across flats, with MJ threads - specifies dimensional requirements for a family of high-strength aerospace nuts. The standard defines the dimensions (in millimetres), configuration and optional features (for example lockwire holes) for nuts used in aerospace product standards. Dimensions apply after any surface coating(s) but before the application of lubricants.
Key tensile-strength and temperature classifications covered include:
- 450 MPa (ambient) / 425 °C
- 600 MPa (ambient) / 235 °C, 315 °C, 650 °C
- 900 MPa (ambient) / 235 °C, 730 °C
- 1 100 MPa (ambient) / 600 °C
ISO 12268:1997 is intended specifically for compiling aerospace product standards.
Key topics and requirements
- Dimensional specification: Exact form, height (reduced), and across-flats reduction for hexagonal plain nuts with MJ threads. All dimensions are given in millimetres.
- Thread type: Nuts are specified for MJ threads; thread tolerances and form/position requirements are referenced to related standards.
- Coating and finishing: Dimensions apply after coatings; surface texture tolerances are noted and manufacturing methods are considered.
- Lockwire provision: Nuts may include holes for lockwire in accordance with ISO 245; the standard notes intended use with lockwire where applicable.
- Tolerances and form/position: Tolerances of form and position are referenced to relevant fastener tolerance standards.
- Use scope: The standard is limited to supporting aerospace product standards rather than general commercial fastener specifications.
Applications and users
ISO 12268:1997 is practical for:
- Aerospace design engineers specifying fasteners for airframe, engine, and high-temperature assemblies.
- Fastener manufacturers producing hexagonal reduced-height nuts with MJ threads to aerospace dimensional norms.
- Procurement and quality assurance teams ensuring supplied nuts meet aerospace product standard dimensions.
- Certification and regulatory bodies verifying compliance with referenced aerospace fastener requirements.
Typical applications include weight- and space-sensitive assemblies where reduced-height and reduced-across-flats nuts are required, and where high tensile strength and elevated-temperature performance are critical.
Related standards
- ISO 245 - Aircraft - Lockwire (holes and use)
- ISO 5855-2:1988 - Aerospace MJ threads - tolerances for nuts
- ISO 8788 - Fastener tolerances (form and position)
- ISO 9139 - Aerospace procurement specification for nuts (referenced for procurement compatibility)
Keywords: ISO 12268:1997, aerospace nuts, hexagonal nuts, MJ threads, reduced height nuts, nut dimensions, aerospace fasteners, lockwire.