Convert 1/4 BSP to 1/4 NPT

[Whiskeymike]

I’m making a couple forge burners and the pieces I bought have a fitting of 1/4” BSP or British Standard Pipe, but everything else I have is NPT. I understand the difference is BSP the threads are cut at 60 degrees and the NPT threads are 55. I’m wondering if I could chase the threads with a 1/4” NPT tap and convert it over. This particular part is just for holding a tube in place, so it does not need to seal for gas purposes.

Anyone know if this is possible or have another idea?

 

[fsae0607]

If it's not for gas sealing, I'd give it a try using your NPT tap.

 

[blazemaster83]

You can also drill it out to the next size up NPT

 

[Muggzy]

I would think that if the thread pitch and diam are is the same, it seems to me;

1) chasing a 55* groove with a 60* groove would blunt the top of the threads slightly
2) chasing a 60* groove with a 55* groove would dig the trough slightly deeper.

If the pitch is not the same, it won't work

Sent from my Pixel XL using Tapatalk

 

[Fix Until Broke]

They're both tapered threads that work on interference - Just screw them together. BSP might be 19 threads/inch vs 18 for 1/4 NPT, but it won't matter. If you're concerned, use some red loctite or JBWeld as thread sealant.

 

[MJD1]

I believe npt and bpt are 1 thread per inch different.

 

[NitroShark]

BSP are 55
NPT are 60

They wont interchange you will need adapter.

 

[The Cobbler]

some reading here. if it's just bracketry, you may get away with your idea. or order a plug or cap on ebay and drill/tap do whatever

https://www.valvesonline.com.au/references/threads/

 

[racingtadpole]

1/4 BSP is 19tpi 1/4 NPT is 18tpi. Attempting to chase it to achieve the correct included angle will ruin the fitting as the number of threads per inch is different.
Any decent hydraulic supplier should be able to supply an adapter, or you can make one using off the shelf fittings if bulk/space isn’t an issue. A quick look on evil says there’s just about every flavour in every material.

 

[Mr. T]

If it doesn’t need to be liquid/gas tight just screw them together. It’ll be fine.

 

[Siegel1719]

McMaster Carr will have every 1/4" NPT to BSP or even BSPP adapter you would ever imagine.

 

[EdT]

In my experience both are tapered threads meant to seal through interference fits. They don't so you have to uses pipe dope. For a purely structural connection. I'd just run an NPT tap into in and call it a day. If it has to seal something, you're on your own. I have personally done it and with some auxiliary sealant it works OK, but I'm not suggesting it as the best approach. As suggested above, adaptors are readily available so that's another possibility.

 

[tonyciambrone]

NPT is not intended to seal through thread deformation... NPTF is but that's a different story.

Just buy an adapter. Never know when you might want to take something apart rather than just ram her home one time and hope for the best like some are suggesting..

 

[Mr. T]

Just buy an adapter. Never know when you might want to take something apart rather than just ram her home one time and hope for the best like some are suggesting..

I mean, in an ideal world, yeah. But I was speaking from experience on this one. While they certainly are different threads, they really are “close enough” that they work together.

It’s not that I prefer it this way or do it out of ignorance but sometimes (at least with my job) the thing has to run. And if all you have is an NPT fitting to go in that BSPT fitting you use some dope and tape and screw them together. Now this is for things like process water and compressed air (80psi and 125psi) so if it would leak a dribble it’s no big deal. I would not recommend doing so for dangerous substances.

So far it’s worked every time without any leaks, some for years.

So for the OP’s situation I maintain that he can just screw them together and it will be fine.

This is also a MUCH better solution than trying to cut the existing threads. That is guaranteed to make things worse in almost every way.

 

[racingtadpole]

The line is carrying a flammable gas, spend the few dollars to get an appropriate adapter. The small cost and time inconvenience isn’t really worth the consequence of the ‘fit we up’ approaches being suggested.

 

[OhioRandy]

All kinds of listing on google search. Get the correct adapter for safety and ease of use.

 

[Fix Until Broke]

The line is carrying a flammable gas...........

..........This particular part is just for holding a tube in place, so it does not need to seal for gas purposes..........

No, it's not - This is what Mr.T and I have been saying. No need to over-complicate this with adapters and such, just screw them together and call it a day.

This is coming from someone who's been injured by the misapplication of 1/4 BSP and 1/4 NPT (and why I know they'll screw together just fine, even with the difference in thread pitch). If this was a sealing application for gas then I'm all in for getting the right adapter or the correct mating part, etc but as the Whiskeymike stated in the first post - it does not need to seal.

Trust me (us) that it'll be just fine!

 

[racingtadpole]

I would still adapt it but that’s just me having a dislike for rough enough is good enough type work but different people have different levels of acceptable.

The take out for me is I really need to stop reading this forum on my phone without my glasses. This getting old thing *****.

 

[Willie Makeit]

NPT is not intended to seal through thread deformation... NPTF is but that's a different story.

Not sure where that info on NPT comes from but the taper on NPT threads allows them to form a seal when torqued as the flanks of the threads compress against each other, thus creating a mechanical seal by way of thread deformation.

 

[Firstram]

I’m making a couple forge burners and the pieces I bought have a fitting of 1/4” BSP or British Standard Pipe, but everything else I have is NPT. I understand the difference is BSP the threads are cut at 60 degrees and the NPT threads are 55. I’m wondering if I could chase the threads with a 1/4” NPT tap and convert it over. This particular part is just for holding a tube in place, so it does not need to seal for gas purposes.

Anyone know if this is possible or have another idea?

Which components of the burner are incompatible? It might not make a difference if it's not gas tight. If it doesn't leak from gas tank to the orifice, it won't matter.

Post a pic of your components