to have no logical sizes that they are based on. I gather that PG is
the German for 'tank thread'.
formatting link
gives the sizes.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