trying to recognise half inch bsp thread

Then it probbaly is. How accurately do you need to know? (It could be a taper rather than parallel thread)

Hi Tec. The OD of 1/2" BSP is just over 21mm. Baz

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Half inch bsp is 14 turns per inch. My source confusingly quotes the dimensions in metric:

Pitch 1.814 Major diameter 20.455 Minor diameter 18.631 (0.73")

Thanks for the help. Usuing a high tech ruler across the ends your metric measurements appear to match my sample. Half inch bsp it is then. I wonder where the half inch size comes from....

Thanks for the help. Usuing a high tech ruler across the ends your metric measurements appear to match my sample. Half inch bsp it is then. I wonder where the half inch size comes from....

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Don't forget to check the pitch as well. Not likely to be anything else but ...

The half inch is the bore of the thick walled iron pipe the male threads are usually to be found on.

The threads formerly known as BSP are now officially metric threads: BS