Overview
ISO 1502:1996 - "ISO general-purpose metric screw threads - Gauges and gauging" specifies requirements for the manufacture and use of gauges used to check ISO general-purpose metric screw threads. The standard defines recommended types of gauges (GO/NOT GO, screw plug, screw ring, plain gauges, calliper gauges), rules for their use, and procedures to distinguish threads that comply with specified limits from those that do not. It is the second edition (1996), technically revising the 1978 edition.
Key topics and technical requirements
- Types of gauges covered: GO and NOT GO screw plug gauges, screw ring gauges (solid and adjustable), plain GO/NOT GO plug and ring gauges, screw calliper gauges, setting plugs and wear check plugs.
- Gauging principles: A workpiece thread must not be delivered if any actual thread size (e.g., pitch diameter) lies outside specified limits; conversely, a purchaser should not reject a thread that lies within limits. Both GO and NOT GO checks are required for limit gauging.
- Inspection roles: Manufacturer and purchaser (inspector) may use different gauges; the inspector should use his own inspection gauges. In disputes, checking of ring gauges by check plugs is decisive unless parties agree otherwise.
- Reference temperature: Dimensions are related to a reference temperature of 20 °C (ISO 1). If gauges and workpieces have different coefficients of linear expansion, both must be at 20 ± 2 °C during gauging or thermal differences must be considered.
- Gauging recommendations: Use screw ring gauges for external threads when possible; screw calliper gauges may be used for convenience but should be supplemented by ring-gauge checks (random sampling). Avoid calliper gauges on non‑rigid parts. Guidance on tolerance zones, profile features, permissible wear and formulae for gauge limits is provided (see standard for detailed tables and figures).
- Avoiding disputes: Grade and distribute gauges (new or slightly worn GO; slightly worn NOT GO) to reduce producer/inspector disagreements.
Applications and users
ISO 1502 is used in:
- Quality control and inspection of metric screw threads in manufacturing
- Calibration and production of thread gauges (gauge manufacturers)
- Metrology laboratories and inspection departments
- Purchasing / acceptance testing to verify interchangeability of threaded parts
Typical industries: mechanical engineering, automotive, aerospace, fasteners, and any sector producing or specifying ISO metric threaded components.
Related standards
- ISO 68 - Basic profile for general-purpose screw threads
- ISO 1 - Standard reference temperature for industrial length measurements (20 °C)
- ISO 1938-1 - Inspection of plain workpieces - Plain limit gauges
Keywords: ISO 1502, ISO 1502:1996, metric screw threads, gauges and gauging, GO/NOT GO gauges, screw plug gauge, screw ring gauge, pitch diameter, thread inspection, metrology, quality control.