SIST EN ISO 228-1:2003 PDF

Overview - EN ISO 228-1:2003 (ISO 228-1:2000)

EN ISO 228-1:2003 specifies requirements for pipe threads where pressure-tight joints are not made on the threads. It covers thread form, dimensions, tolerances and designation for fastening pipe threads from size 1/16 to 6 inclusive. Both internal and external threads are parallel (not tapered) and intended for mechanical assembly of fittings, cocks, valves and accessories. Where a pressure-tight joint is required, sealing must be achieved outside the threads by compressing mating faces and using an appropriate seal.

Key topics and technical requirements

• Thread scope: Fastening (non-jointing) parallel pipe threads, sizes 1/16–6.
• Thread form and geometry: Full and truncated profiles defined; fundamental triangle and profile dimensions are specified (examples: H, h, r are proportional to pitch P).
• Dimensions and tolerances: Detailed numerical dimensions and tolerance zones are provided in Table 1 (millimetres). Tolerances include:
  • Pitch, major and minor diameters for internal and external threads.
  • Two external pitch-diameter tolerance classes: Class A (tighter) and Class B (wider).
• Designation rules: Formal designation format (e.g., “Pipe thread ISO 228 - G 1 1/2”, with optional A or B for external tolerance class; add “LH” for left‑hand threads).
• Right-hand/left-hand: Threads are right-hand by default; left-hand threads are designated with “LH”.
• Combining with jointing threads: Special considerations apply when combining G (parallel) external threads with Rp internal threads (ISO 7-1); such combinations do not necessarily give a leaktight joint.
• Verification and gauging: ISO 228-2 gives methods for verification by limit gauges and recommended gauging systems.

Practical applications and users

• Useful for manufacturers and designers of pipe fittings, valves, cocks, and plumbing accessories where mechanical fastening (not thread sealing) is required.
• Applied by:
  • Mechanical and piping engineers specifying thread interfaces.
  • Production and quality engineers using gauging and inspection criteria.
  • Standards writers and product specification teams selecting appropriate tolerance classes (A or B) based on assembly and functional needs.
• Typical use cases: assembling modular fittings, non‑pressure mechanical connections, and components where sealing is provided by gaskets, O‑rings, or face seals outside the threads.

Related standards

• ISO 7-1 / prEN 10226-1/2 - pipe threads where pressure-tight joints are made on the threads (jointing threads).
• ISO 228-2 - verification by means of limit gauges (recommended gauging and verification methods).

Keywords: EN ISO 228-1:2003, pipe threads, parallel threads, thread dimensions, tolerances, designation, fastening threads, tolerance class A B, ISO 228-2, ISO 7-1.