Overview
ISO 2009:2011 specifies the characteristics of slotted countersunk flat head screws - Product grade A with metric external threads from M1,6 to M10 inclusive. Published by ISO in 2011 (fourth edition), the standard defines dimensions, tolerances, material/property class options, surface treatments, acceptance inspection and designation conventions for these common countersunk screws used in mechanical assemblies.
Key topics and requirements
- Scope: Applies to slotted, countersunk flat head screws of product grade A with threads M1,6–M10.
- Dimensions: Head, thread and shank dimensions are given (see Figure 1 and Table 1 in the standard). The shank diameter is approximately equal to the pitch diameter or may equal the permissible major thread diameter. Nominal head and thread lengths and preferred lengths are identified.
- Thread and tolerance: General-purpose metric threads are referenced to ISO 261 and ISO 965-2. Tolerance class for external threads is 6g (as specified).
- Materials and mechanical properties: Steel fasteners (property classes 4.8, 5.8), stainless steel (A2-50, A2-70) and non‑ferrous options are covered with references to ISO 898-1, ISO 3506-1 and ISO 8839 for mechanical properties.
- Surface finishes and coatings: Electroplating and passivation requirements reference ISO 4042 and ISO 16048. Non‑electrolytically applied zinc flake coatings are covered by ISO 10683. Additional finishes are agreed between supplier and purchaser.
- Quality and inspection: Surface discontinuity limits and acceptance inspection procedures are specified via ISO 6157-1 and ISO 3269. Tolerances for product grade A are referenced to ISO 4759‑1.
- Designation: Example format - “Countersunk flat head screw ISO 2009 - M5 × 20 - 4.8”.
Applications and users
ISO 2009:2011 is practical for:
- Fastener manufacturers ensuring consistent production of slotted countersunk screws.
- Design and mechanical engineers specifying screws for assemblies requiring flush mounting.
- Procurement and quality inspectors verifying compliance with dimensional, material and surface treatment requirements.
- OEMs, electronics, automotive and machinery sectors that use small to medium metric countersunk screws (M1,6–M10).
Using this standard helps ensure interchangeability, predictable mechanical performance, and consistent finishing/inspection practices across suppliers.
Related standards
Commonly referenced companion standards include: ISO 225, ISO 261, ISO 965-2, ISO 898‑1, ISO 3506‑1, ISO 4042, ISO 4759‑1, ISO 6157‑1, ISO 3269, ISO 10683 and ISO 16048. These help specify thread forms, tolerances, mechanical properties, coatings and inspection methods tied to ISO 2009:2011.
Keywords: ISO 2009:2011, slotted countersunk flat head screws, product grade A, M1.6 to M10, fastener standards, countersunk screws, metric threads.