[Arivaldo]

I hope this is useful...

Originally Posted by Der Brewling

I didn't see anything addressing common size ratings on various types of threads on pipe fittings specifially, so I found a few links.

British and other sizes:
http://mdmetric.com/tech/thddat7.htm

And standard American:
http://mdmetric.com/tech/thdform3.htm

That site also has other national standards on it as well.

British Pipe Thread ( Whitworth Form) -- Parallel (BSPP/BSPF)
(important spec.) G 1/4 Parallel Thread - Nominal Size = 1/4" - 19 Threads per inch



Others specs.: Major Diameter d=D 13.157 mm --- Minor Diameter Male Thd. - d3 = 11.445 mm --- Tap Drill Diameter = 11.6 mm --- Included Thread Angle = 55 deg --- Pitch - p = 1.337 mm

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NPT Tapered Pipe Threads
(important spec.) Tapered Threads - Nominal Size 1/4" NPT - 18 Threads per inch



Others specs.: Taper Angle = 1 deg 47' --- Pipe O.D = 0.540" = 13.716 mm --- --- Included Thread Angle = 60 deg --- Pitch - p = 0.0556" = 1.412 mm