BSP nuts on a NPS thread

[5010m0n]

Hi all

Here's the situation - I'm building a brewery and I'm following instructions found on this page
http://www.theelectricbrewery.com/heating-elements?page=7


Basically, the heating element is inserted through the skin of the brewing vessel and a seal is provided by a silicone o-ring on the outside. A nut is then used on the inside to hold the element in place.

Thing is, I'm in the UK and I'm ordering these products from the US so all the threads and such are NPS... the only thing I can't easily source from the US is the nut that holds the element on the inside.

I appreciate that the NPS and BSP standards are fairly close but they are sufficiently different for them not to be compatible.... however I've read one website saying you shouldn't use them together if a good seal is required...

This begs the question, considering the seal is provided by the silicone o-ring on the outside and all I need to do is to do is find a nut that will hold the element in place firmly, can I use a nearly-compatible BSP nut on the NPS thread?

Cheers!

 

[Burnerman]

It all depends on how easily the threads mate together..... Will they cross thread and be very difficult to run up, or will the threads jump once they are tightened? In this case I'd give it a go, I think as the finished join wouldn't need to be too tight.
John

 

[5010m0n]

That's pretty much my thought - I just wondered if anyone has had experience of doing this - it's surprisingly difficult to find this information on the web.

 

[Burnerman]

You would be 5 deg out on the included pitch angle......not much really on a large diameter thread and particularly so on soft metal.
BSP threads have a rounded root whilst the other one would be flat (I think that's right).
NPT threads would be tapered male and you don't want that one!
John

 

[Richardthe3rd]

You may find this link useful;
http://www.malonespecialtyinc.com/Identifying_Threads.html

 

[5010m0n]

Thanks guys...

Alrighty, so NPS has a 60deg angle on its threads, and BSP has a 55deg angle. and both appears to have 14 threads per inch... I figure this means that my BSP nut will fit my NPS heating element with a little BFI (Brute Force and Ignorance )

My elements will still be another few weeks to be delivered from the US - in the meantime I'll get a few BSP nuts and I'll come back to let you know how I get along. I really don't want to have to source nuts from the US and wait another couple of weeks for their arrival!

 

[5010m0n]

I can confirm that my 1" BSP nut does indeed fit onto my 1" NPS thread.

I'm have no idea whether this is a watertight fit, or whether it can be made watertight with PTFE tape, but I don't need it to do that - I just need a solid, non-slip, and positive fit... which it achieves.



Happy now.