IEC 60399: Control Gauges for Lampholders and Caps — The “GO/NO-GO” Test for Lamp Interchangeability

Every E27 Bulb Fits Every E27 Socket — The GO/NO-GO Gauge System Behind Global Lamp Interchangeability

IEC 60399:2008 specifies control gauges for lampholders and caps — the quality inspection tool ensuring billions of lamps and lampholders worldwide are interchangeable. Every lampholder and cap must pass GO and NO-GO gauge inspection before leaving the factory.

GO/NO-GO principle: The GO gauge represents the Maximum Material Condition (MMC) — the cap must screw smoothly into the GO gauge, proving it is “not too large.” The NO-GO gauge represents the minimum material condition — the cap must not enter the NO-GO gauge (or enter less than 2 turns), proving it is “not too small.” Only caps passing both GO and NO-GO are guaranteed to fit reliably in all brands of lampholders.

TNLab — GO/NO-GO gauging is manufacturing oldest, simplest, and most reliable quality control method. IEC 60399 standardized it for lamp interchangeability.