Overview
ISO 3186:2008 specifies the dimensions and related dimensional requirements for large bihexagonal‑head bolts used in aerospace applications. It covers bolts with normal shank (close or large tolerance), short or medium length MJ threads, made of metallic material (coated or uncoated), and strength classes 1 250 MPa to 1 800 MPa. The standard is intended for inclusion in aerospace product standards and replaces the 1994 edition.
Key topics and technical requirements
- Bolt configuration and dimensions: Detailed geometry is defined by Figure 1 and Table 1 in the standard (major/minor diameters, head geometry, thread length L, grip/shank details).
- Thread form and series: MJ thread forms and limits are referenced and coordinated with ISO 5855-2 and ISO 3353-1 for rolled external threads.
- Tolerances and fits: Dimensional tolerances and tolerances after coating are specified in millimetres; hole and shaft tolerance grades (e.g., H13, h6) conform to ISO 286-2. Tolerances of form and position refer to ISO 7913 unless otherwise stated.
- Coatings and measurement: Dimensions apply after any coating is applied (with specific pre‑coating shank tolerances noted for heat‑cured organic matrix coatings). Measurements are taken before lubricant application.
- Wrenching and drive details: Wrenching configuration and drive dimensions align with ISO 4095 for bihexagonal drives.
- Strength classes: Bolts in the scope are explicitly limited to 1250 MPa – 1800 MPa, covering high‑strength aerospace fasteners.
Applications and users
- Aerospace design engineers specifying fasteners for airframes, engine mounts, landing gear, and structural assemblies.
- Fastener manufacturers and suppliers producing MJ‑threaded, bihexagonal‑head bolts to aerospace dimensional requirements.
- Quality assurance and inspection teams performing dimensional checks, acceptance sampling, and conformity verification.
- Procurement and maintenance organizations ensuring parts ordered or replaced meet aerospace product standard dimensions and tolerances.
- Standards writers and certification bodies incorporating bolt dimension requirements into aircraft product standards and technical specifications.
Related standards
- ISO 5855-2 - MJ threads limit dimensions for bolts and nuts
- ISO 3353-1 - Rolled external threads (lead and runout)
- ISO 4095 - Bihexagonal drives - wrenching configuration
- ISO 286-2 - Limits and fits (tolerance grades)
- ISO 7913 - Tolerances of form and position for aerospace bolts and screws
Keywords: ISO 3186:2008, aerospace bolts, bihexagonal head bolts, MJ threads, bolt dimensions, aerospace fasteners, 1250 MPa, 1800 MPa, ISO standards.