ISO 7-2:2000

Overview

ISO 7-2:2000 - "Pipe threads where pressure‑tight joints are made on the threads - Part 2: Verification by means of limit gauges" defines a standardized gauging system for verifying pipe threads using limit gauges. It specifies procedures and gauge types to validate taper internal and external threads and parallel internal threads whose dimensions and tolerances are given in ISO 7-1. The standard helps manufacturers, inspectors and calibration labs confirm that threaded pipe fittings meet the dimensional elements needed for pressure‑tight threaded joints.

Key topics and requirements

• Scope of verification: Uses limit gauges to check major diameter, pitch diameter at the gauge plane, and accommodation length for internal taper/parallel threads (as defined in ISO 7-1).
• Gauge types defined: Includes taper full‑form threaded plug gauges (Nos. 1 & 2 - 1:16 taper), parallel full‑form threaded ring gauge (No. 3), taper plain ring gauge (No. 4), taper modified form check plug (No. 5) and parallel modified form check ring (No. 6). Annex A lists gauge summaries and identification numbers.
• Design and use: Details on gauge design, marking (positive/negative faces), tolerance steps, and use procedures are provided (clauses 5–6). The 1:16 taper allows representation of maximum and minimum limits by axial tolerance steps.
• Gauge lifecycle control: Specifies manufacturing tolerances, methods for checking new gauges, permissible wear allowances, and marking/identification rules (clause 7).
• Limitations: The gauging system does not replace all quality controls. Additional checks (tool control, visual inspection, direct measurement of useful thread length) are required. Gauging may be unsuitable for injection‑moulded plastic parts without special precautions.
• Legal/contractual note: In disputes about compliance with ISO 7-1, the gauges specified in ISO 7-2 are considered decisive for the thread elements they control.

Applications and who uses it

• Quality control and inspection of pipe fittings, valves, and threaded components used in plumbing, heating, gas, and industrial piping systems.
• Gauge manufacturers and calibration laboratories producing and certifying limit gauges for pipe threads.
• Production engineers, metrology teams, and procurement/specification writers who need consistent thread gauging and acceptance criteria for pressure‑tight threaded joints.
• Third‑party inspectors and compliance bodies resolving disputes about thread conformance.

Related standards

• ISO 7-1:1994 - Dimensions, tolerances and designation for pipe threads where pressure‑tight joints are made on the threads.
• ISO 7 (general): consists of Part 1 (dimensions) and Part 2 (verification by limit gauges).

Keywords: ISO 7-2, pipe threads, limit gauges, taper threads, thread gauging, gauge calibration, pipe fittings, pressure‑tight threaded joints.