Very tapered pipe thread: anyone know what it is?

[jdc]

I wonder if anyone knows what thread the one on the top is? It's 14 tpi and I think is the same thread form as 1/2" BSP, but the taper is much greater than the 1 in 16 of BSPT, as can be seen by comparing it with the example of 1/2" BSPT on the bottom in the photo.

It's on a gas bottle, so maybe '17E' but I can't find a dimensioned drawing or spec for this (nor for 25E which I'd also like) except if I buy ISO 11363 for >£100, which is rather a lot on the off-chance it is described within!

 

[DinghyMan]

1/2" 14 NGT thread

W19.8, 17E:
Small end minor diameter 17.4mm
Taper on diameter: 3:25
Thread angle: 55 degrees
Threads per inch: 14
Specs:
Type 2 Size 1 of IS 3224 : 2014
Equivalent to 19.8 mm of DIN 477-1 : 1990, E 17 con of EN 144-1 and 17E of EN ISO 11363-1


from https://law.resource.org/pub/in/bis/S08/is.3224.2002.pdf

 

[jdc]

Many thanks for the copy courtesy of the Indian standards body. From that I gather that it can't be 17E as its taper is only 1:16. Others are 1:8 or 3:25, but not that small a diameter, so I still don't know what my thread is.

 

[colhel]

It could be NPTF (national pipe taper fuel). This has an inclusive angle of 8 degrees which is just over double bsp which is about 3.5 degrees (1:16). The idea of the larger taper is so it seals without the use of sealant. Possibly the female part will be tapered too.

 

[plumbob]

Looks like the valve off the top of a gas bottle to me.?

 

[WoodyP]

Looks like the valve off the top of a gas bottle to me.?

Read the OP again