ISO 228-2:1987

Overview

ISO 228-2:1987 - "Pipe threads where pressure‑tight joints are not made on the threads - Part 2: Verification by means of limit gauges" specifies how to verify cylindrical pipe threads (the dimensions/tolerances of which are given in ISO 228-1) using limit gauges. This second edition (1987) cancels and replaces the 1980 edition. It addresses verification for the 55° thread profile and defines the required GO and NOT GO gauges, wear checks and inspection practices needed to confirm pitch diameter, major/minor diameters and profile form.

Key topics and technical requirements

• Scope: Verification procedures for cylindrical pipe threads used where sealing is not made on the threads.
• Gauge types:
  • Solid threaded GO ring gauge and NOT GO ring gauge (external threads).
  • Threaded GO plug and NOT GO plug (internal threads).
  • Wear check plugs to assess allowable gauge wear.
  • Multiple GO and NOT GO checks are required due to the 55° profile elements.
• Functional checks:
  • GO gauges verify the maximum‑material limit (virtual pitch diameter) and form (including rounding at crest/root and flank length).
  • NOT GO gauges verify the minimum material limit of the pitch diameter.
  • Wear checks embody the pitch diameter at a prescribed wear limit and are used for periodic control.
• Use/control rules:
  • Gauging is typically performed by hand without excessive force; entry depth limits (number of turns) are specified for pass/fail criteria.
  • Checks follow the Taylor principle for gauging virtual pitch diameter (as referenced to ISO 1502).
• Tolerances and classes:
  • Numerical tolerance values and gauge dimensions are provided (separate tables for class A and class B threads and values dependent on pitch).
  • Pitch tolerance and other dimensional limits are specified for reliable inspection.

Applications and who uses it

• Practical for manufacturers, quality inspectors and calibration labs that produce or inspect threaded pipe fittings and connectors where sealing is not made on threads (e.g., mechanical assemblies, conduits, instrumentation fittings).
• Useful in industrial production, maintenance, metrology and acceptance testing for thread conformity.
• Applies to suppliers and purchasers who require standardized gauge verification procedures for threaded components.

Related standards

• ISO 228-1 - Designation, dimensions and tolerances for cylinderical pipe threads (reference normative dimensions).
• ISO 1502 - General purpose metric screw threads - Gauging (Taylor principle).
• ISO 1179 - Example industrial application for pipe connections to ISO 228.

Keywords: ISO 228-2, pipe threads, limit gauges, GO gauge, NOT GO gauge, threaded ring gauge, threaded plug gauge, wear check plug, pitch diameter, thread verification, ISO 228-1.