Measuring an adapters size

jsmoke · 27 Mar 2021 at 18:19

I bought this adapter.

https://www.screwfix.com/p/pcl-stan...jAg77h5QzzAc1cOEufhoCY7UQAvD_BwE&gclsrc=aw.ds

I was expecting the threaded diameter to be 1/4'' or 6.35mm but when I measure with digital calipers it's close to 12.7mm which is 1/2''.

Am I misunderstanding the dimensions of this adapter or did I get the wrong adapter?

rodders · 27 Mar 2021 at 19:16

What you going into, another 1/4bsp thread or an 1/8?
You can look up BSP dimensions online easily enough.

andy_mk3 · 27 Mar 2021 at 19:21

1/4" BSP will measure at 1/2"

peige · 27 Mar 2021 at 19:26

The size is based on in internal diameter of the steel pipe they used to suit but thats all a bit out the window now. A quick google will show you the size of each thread.

andy_mk3 · 27 Mar 2021 at 19:27

PS what are you using the adapter for? If it's air hose then 1/4 BSP is the standard fitment.

jsmoke · 27 Mar 2021 at 19:29

no idea what said:
1/4" BSP will measure at 1/2"

Ah I don't about BSP fittings and sizes that explains it. First I've come across this.

Hotwired · 27 Mar 2021 at 19:40

Better to think of traditional pipe sizes as names not an actual measurement.

Plus it was originally the inside diameter of a (1/4") pipe which is obviously smaller than the outside diameter of a 1/4" pipe and that has to be smaller than a fitting which goes around the 1/4" pipe.