PG Threads

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'.
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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
Reply to
Andrew Mawson
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They are a right bastard. They were introduced to take over from conduit thread but have now been dropped and we have gone onto metric conduit threads which by pure chance happen to be the same as the earlier conduit threads.
As you have found out they are a right mismatch. Metric O/D's but that pitch of 1.41 actually [ not 1.51] is actually 18 tpi.
Just to throw another wobblie the pitch angle of the thread is 80 degrees.
Obviously designed by a European committee sitting in 10 countries sharing 12 languages and 1/2 a brain.
Try buying a tap, the two popular ones PG9 and PG16 have prices of between £45 and £60 per tap.
Here's a good page on the specs.
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Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:-
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Reply to
John Stevenson
Most electrical wholesalers stock adapter couplings and bushes but of course they also stock pg fittings. Mark
Reply to
mark
female
Sadly not locally Mark, and even Newey & Eyre couldn't supply. Still job done now.
AWEM
Reply to
Andrew Mawson
PG stands for "Panzer Gewinde". That would translate to "tank thread", but it has nothing to do with tanks. Panzer is simply something that is protected, shielded, rugidized. The origin is from electrical installations and belongs to the "Stapa-Rohr" ("Stahl Panzer Rohr", what translates to "steel 'tank' tube"). That tube is simply a protection of electrical conduits.
If you want to know about the geometry, I can look that up for you.
Nick
Reply to
Nick Müller
Good site for pg info
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We must be spoilt up here Andrew,local wholesaler with good range of pg/metric adapters and next door to him Telemechanique distributor.
Thought for the day:- We used to have an empire that was run by an emperor. Then we had a kingdom that was run by a King. Now we have a country-----
Mark
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mark

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