Overview
ISO 885:2000 - General purpose bolts and screws - Metric series - Radii under the head specifies the required sizes of the radii under the head and the transition diameters for metric-series general purpose bolts and screws. This second edition (2000) replaces the 1976 edition and provides dimension tables and an illustrative figure to ensure consistent head-to-shank junction geometry across manufacturers and users.
Key topics and requirements
- Scope: Defines radii (r) under the head and the transition diameter (d) at the junction of the radius and the bearing surface of the head.
- Dimensional coverage: Includes metric thread diameters from 1.6 mm up to 36 mm (see Table 1 in the standard).
- Reference figures and tables: Figure 1 illustrates the geometric relationship; Table 1 lists the required values for r and d including differentiation by product grades (A, B, C) where applicable.
- Standardization purpose: Ensures reproducible head geometry for compatibility, predictable bearing surfaces, and controlled stress concentration at the head–shank junction.
Applications
This standard is useful for professionals involved in the design, manufacture, procurement and quality control of fasteners:
- Mechanical and design engineers: Use ISO 885 to specify correct head radii and transition diameters in assemblies to reduce stress risers and ensure seating integrity.
- Fastener manufacturers: Apply the dimensions for tooling, die design and quality checks to meet international conformity.
- Quality inspectors and testing labs: Verify that supplied bolts and screws conform to the radii and transition diameter limits in Table 1.
- Procurement and specification writers: Reference ISO 885 in purchase orders, drawings and part specifications to ensure interchangeability and consistent fit.
- CAD and CAM modelers: Model accurate head-to-shank transitions for simulations, interference checks and automated manufacturing setup.
Practical benefits
- Improved interchangeability across suppliers and regions.
- Reduced failure risk by controlling geometry that affects fatigue and bearing behavior.
- Streamlined manufacturing through clear dimensional targets for tooling and processes.
- Clear acceptance criteria for inspection and supplier qualification.
Related standards
ISO 885 was prepared by ISO/TC 2 (Fasteners), SC 7 (Reference standards). It complements other ISO fastener standards covering terminology, dimensioning, sizes and tolerancing. For complete specification, refer to ISO 885:2000 itself (Figure 1 and Table 1) and related ISO fastener documents.
