Wikipedia
The Stahlpanzerrohrgewinde standard for screw threads, more often called by the shorter name Panzergewinde (pronunciation), is a technical standard created in Germany and subsequently used in various countries, such as the German-speaking zone (Germany, Switzerland, Austria) and neighboring European countries. The German name "Stahlpanzerrohrgewinde" translates to English as 'steel (pipe armoured) conduit thread'. The thread is used to join pieces of electrical conduit and cable glands.
Alternative stylings of the German name are Stahl-Panzer-Rohr-Gewinde and an abbreviated form, StaPa-Rohr-Gewinde.
The standard, codified by the Deutsches Institut für Normung (DIN, German Institute for Standardization), is DIN 40430. Panzergewinde sizes are named with the prefix PG plus a nominal number which approximately corresponds to the maximum cable diameter (in millimeters) that can be passed through the conduit.
Because the walls of the conduit are usually relatively thin, the thread depth should not be very large. Thus a thread angle of 80° is used. The Verband der Elektrotechnik, Elektronik und Informationstechnik (VDE) (which began as a trade association for standardization in electrical engineering) originally standardized (and named) the thread for use with conduit and cable glands that were made of steel, although today the thread is used with both steel (typically plated with combinations of nickel, zinc, or tin to resist rusting) and polyvinyl chloride (PVC).
Beginning in 2000, the VDE standard for cable glands (VDE 0619) was formally replaced by EN 50262. After a transitional period of several years during which it could still be used, it was replaced in 2003 by a final metric fine thread with pitch. Similarly, conduit threads were replaced by EN 60423.
Even today, Panzergewinde cable glands are still often found on chemical reactors and bioreactors (for example, PG13.5 thread for screwing in sensors) and various other equipment, enclosures, junction boxes, and connectors.