On Fri, 22 Sep 2006 17:09:59 +0100, Roger
wrote:

The message
from Matt contains these words:

Is it 1/2 " bsp or metric?

BSP is an ISO standard thread, which makes it officially a metric thread.

Are you *really* sure of that?

My now rather old reference states:

"British Standard pipe threads are recognised by ISO and are maintained
in the inch system with fractional designations for pipe joints."

The dimensions in the tables are metric apart from TPI.

Currently being nowhere near my usually easily accessible Zeus
tables/Kempes/Machinery's Handbook i'll take your word for it!

Bloody strange state of affairs when it has to be dimensioned in
metric though. Probably to suit the Germans/French who couldn't devise
a sensible thread if their life depended on it. PG threads used (or
not) for conduit/industrial switchgear are one of the most obscure.

They have a Metric OD (but ridiculously referenced so that PG 13.5 is
actually just over 20mm, not exactly 20mm mind as that would be far
too sensible - (20.4mm to be exact), 18tpi pitch which equals 1.41mm
yes 1.41mm, not 1.5mm as that might remotely make some sense and an 80
degree thread angle so they can't be cut using common off the shelf
tooling.

Why on earth would any sane person bother with PG crap when 20mm or
larger conduit holes can be punched for 1/10 Euro cent and use
standard conduit fittings that have been around for three decades?


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