trying to recognise half inch bsp thread

[technical123]

I have an old plumbing elbow, female both ends, it looks like half inch bsp to me but is there a way to double check please. Just for info it will thread on to a 15mm compression joint thread. Thanks

PS The inside diameter is about three quarters inch

[John Stumbles]

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

[Baz]

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

[Roger]

The message from " [e-mail]" contains these words:

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")

[technical123]

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....

[technical123]

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....

[Roger]

The message from " [e-mail]" contains these words:

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.

[Andy Wade]

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

21:1985 and EN 10226-1:2004 give the dimensions in metric units. Many dimensions may just happen to be simple multiples or sub-multiples of 25.4, but that's just a coincidence ;~)