Losing the thread

From the year 2000, only cable screw couplings with metric threads can be designed or used in new products. This will apply to all conduit entries, for example in switch cabinets, distribution casings, surface mounted boxes, domestic connection boxes, installation sockets and equipment casings. The familiar PG7 and PG48 sizes will be replaced by M12 to M63 threads, while additional sizes from M6 to M75 have also been included in the new EN standard.

Given the large user base of PG design threads, the industry is being given time to adjust to the changeover. While EN 50262 takes effect from the end of December, PG cable screw couplings can be supplied as replacements for existing products until the end of March 2001. Alongside the old VDE 0619, the current test standard for PG cable screw couplings will also be withdrawn.

The introduction of the new standard will mean that threads throughout Europe and the Commonwealth will be uniform, though it will not be an international standard as the USA continues to use imperial standards. However, while the USA is not adopting the metric thread, we have noted an increasing demand for such products.

Another benefit is that EN 50262 is a safety standard, not just a construction standard, stipulating dimensions like the old DIN 46319 or DIN 46320. The only dimensional condition in EN 50262 relates to the interface of screw coupling to casing, the thread or bore, giving freedom when designing gland functions.

Yet the demand so far for metric threads in the light of impending change has been below our expectations. This, we believe, is mainly the result of a lack of information about the conversion, perhaps not surprising since EN 50262 was only published in March. Despite an apparent resistance to change from European users, the PG thread's days are numbered.