Anyone know the origin of the German PG electrical threads? They seem to have no logical sizes that they are based on. I gather that PG is the German for 'tank thread'.
I got caught today inatalling a new pump motor (made 2002 so not Imperial sized) - connection box had two moulded in but blind female threads to take the input cable gland, and as they were too large for a standard 20mm I ASSUMED that they were 25mm conduit thread, and happily went and turned a 20 -> 25mm converter bush. Of course it wouldn't screw in - too big. Turns out the female threads are PG16 with that nice standard of 22.5mm o/d and 1.51mm pitch ! A 25mm x
1.5mm set of chasers in a 1" die head closed down to 22.5 ok and over the 4 threads engaged the difference between 1.5mm & 1.51 isn't an issue - but what odd sizes they are!!!AWEM