Overview
ISO 10642:2019 specifies the characteristics of hexagon socket countersunk head screws with reduced loadability. It applies to steel and stainless-steel screws with metric coarse pitch threads M2 to M20, product grade A, and defines head geometry, gauging, dimensional limits and related mechanical-property requirements. The standard emphasizes that these screws have reduced ultimate tensile load because of their countersunk head design and the penetration of the hexagon socket.
Key topics and requirements
- Scope and materials: Covers steel (property classes 8.8, 10.9, 12.9) and stainless steels (A2/A4 family with various property classes noted in ISO 3506-1).
- Dimensions and head configuration: Detailed head geometry, socket forms (including broached socket alternative) and reference dimensions for M2–M20 are specified; head height k and internal-drive depth t are included.
- Reduced loadability: The head design combined with socket penetration limits the screw’s ultimate tensile load (see Table 5 of the standard). Users must consult the standard for minimum ultimate tensile loads and limitations.
- Gauging and flushness: Gauge dimensions and flushness checks (gauge surfaces A and B) are defined to control head-bearing surface relation and assembly fit.
- Thread and tolerance requirements: Metric coarse pitch threads per ISO 965-1 with tolerance class 6g; partial/fully threaded length rules and reference threaded lengths (notably b ≥ 3d for partially threaded M14–M20 to allow tensile testing).
- Marking, labelling and acceptance: Requirements for product marking, package labelling and acceptance inspection refer to ISO acceptance standards.
- Coatings and surface integrity: Guidance on coatings (ISO 4042, ISO 10683) and surface discontinuity limits (ISO 6157 series).
Applications and users
ISO 10642:2019 is practical for:
- Fastener manufacturers and tooling designers producing hexagon-socket countersunk screws to specified dimensional and gauging limits.
- Design engineers specifying flush-head screws where limited tensile load is acceptable or required for the application.
- Quality, inspection and procurement teams verifying compliance, dimensions, marking and acceptance criteria.
- Assemblers and maintenance engineers where correct bearing-surface alignment and countersink fit are critical to joint performance.
Typical use cases include applications requiring a flush head with internal drive and known mechanical limitations - for example in machinery panels, enclosures and assemblies where aesthetic or flush mounting is required and tensile loading is controlled.
Related standards
Normative references and complementary standards include:
Keywords: ISO 10642:2019, hexagon socket countersunk head screws, reduced loadability, M2–M20, product grade A, gauge, dimensions, tensile load, stainless steel.