What Do We Call This Inside/Outside Thread/Pipe Matching thing?

[abrogard]

I seem to have two 1/2" pipes I need to join. Now one has thread on the inside and the other has a thread on the outside.

But internal diameter they'd both be 1/2" pipe I reckon.

I think this is probably a very common thing with a very common way of dealing with it - perhaps even a common way of referring to it that I'm ignorant of.

Is there something?

[Wrongwayfirst]

As in life threads are the same. Threads on the outside of pieces are male threads and threads on the inside of pipes etc are female threads.

to my recollection pipes are not normally threaded internally as the nominal thread sizes are so called because of the relative nominal pipe size. Fittings however can be threaded internally and externally.

so in pipe speak. When talking water - Pipes almost always are a male thread, thread on the outside. Eg 1/2” is a nominal size on galvanised pipe, copper pipe, pvc pipe and poly pipe they may all be called 1/2” but will all have different OD (outside diameter) but all will take or have a connection to take a 1/2” BSP thread (British Standard Pipe/Pitch)

windmill pipe is BSW ( British Standard Witworth) generally a solid rod joined with a socket (rod male thread - socket female thread both ends) I have seen pipe used as “rod” and farmers are an ingenious lot and I have seen pipes threaded internally but not BSP.

pictures are always helpful when you do not know the names of things and need assistance.

cheers

[abrogard]

Ah... thanks for that. So generally all threads are on the outside of a pipe and the inside of a fitting?

I didn't know that. That's a good clue, if true.

So the ID is the nominal pipe dia and with different thickness pipe walls we'd get different OD. So how do they manage to make all threads fit with different OD's for the same nominal pipe size?

I thought this feature would be the same with all kinds of pipes and everywhere. Never occurred to me that this 'pipe threads on the outside' thing would mean it's a no-go, really, doesn't/shouldn't happen.

But it's happening with this gas fitting I've got here. It seems. Maybe because one of the 'pipes' is a braided flexible hose and has the thread on the inside, so to speak. Not really. But in effect. Because the hose finishes with a loose connecting nut and the thread is inside it. I suppose that counts as 'a fitting' really? And the answer is going to be an adapter fitting.

Here's a pic:

two pipes.jpg

[Bohdan]

So the ID is the nominal pipe dia and with different thickness pipe walls we'd get different OD. So how do they manage to make all threads fit with different OD's for the same nominal pipe size?

It's the other way around.

All pipes are the same OD with the pipe thickness changing the ID.

That's why the pipe size is a "nominal" dimension based on the ID.

[AJ.]

Yes a picture tells a thousand words and the fact that we are talking about gas fittings and its hose rather than pipe makes all the difference.

Certainly no expert here but I reckon what you are after is called an adaptor. something like this Gasmate Brass Gas Adaptor Converts 1/4" BSP to 3/8" BSP - Bunnings Australia probably not the correct size for you but you get the idea and what to search for.

Cheers Andrew

[abrogard]

Oh. I got it wrong way round again. Okay, thanks.

I'm thinking I maybe need a converter 1/2" to 3/4".

They don't seem to sell that though. And I imagine they sell what's normal everywhere and I'm talking normal. ie. normal mass product in Aus., normal braided LPG fitting. There must an adapter thing I'm not aware of yet....

Like a detective story isn't it?

[Bohdan]

Just to throw another spanner into the works.

A lot of gas LPG fittings are a left hand thread and would not be available in your average store.

[abrogard]

Yep. That elbow was LHT when it screwed into the gas hob pipe. Bur the free end I'm looking to hook onto seems to be RHT.

[jack620]

Your brass elbow appears to be ½" BSPT (British Standard Pipe Taper). I don't believe you will find a fitting that adapts ½" BSPT to an LPG BBQ hose kit. That's not because there's no market for them. It's because they don't want clueless people mistakenly connecting an LPG bottle to a natural gas appliance.

I tried to find one when I helped my dad convert his old Metters stove to LPG. In the end I had to manufacture an adapter from two fittings and a short length of ½" copper pipe.

[Wrongwayfirst]

From the photo - guessing- elbow has 1/2” male bsp and you need to connect the regulator and hose which is probably 3/8” female.

stick them both under your arm and head off to a camping shop, plumbing shop and Bunnings - in that order as camping shop 5 minutes and may have it in one fitting, plumbing shop 5 minutes and may have one perhaps two fittings and Bunnings 15 minutes and probably 3 or more fittings.

I also hope you heeded the advice in your other thread and checked the hob gas type and made sure it is LPG or Propane and not Natural gas.
cheers

[Wrongwayfirst]

Your brass elbow appears to be ½" BSPT (British Standard Pipe Taper). I don't believe you will find a fitting that adapts ½" BSPT to an LPG BBQ hose kit. That's not because there's no market for them. It's because they don't want clueless people mistakenly connecting an LPG bottle to a natural gas appliance.

I tried to find one when I helped my dad convert his old Metters stove to LPG. In the end I had to manufacture an adapter from two fittings and a short length of ½" copper pipe.

not entirely true there are many fittings that connect 1/2” BSP to Flexi gas hoses. It is true there are not many that connect BSP to Primus thread or to left hand threads, but for what OP needs you just have to go to the right place. You won’t find many fittings in Melbourne CBD but you will find them all over country Victoria.
cheers

[abrogard]

Okay. I'll take the elbow off and arm myself with a photo of the whole thing then go to the local camping shop. Good idea that I think.

The hose is actually specified in the manual but not so's it's useful to me.
It says 'Can be connected with a Flexible Hose which complies with AS/NZS 1869 (AGA Approved), 10mm class B or D, no more than 1.2m long and in accordance with AS5601.'

It also states the gas inlet is 1/2" BSP, which we know and which I've purchased an elbow and screwed it in as per their diagram. So now what I'm trying to deal with is the 'other end' of that elbow. Also 1/2" BSP I suppose.

[jack620]

So now what I'm trying to deal with is the 'other end' of that elbow. Also 1/2" BSP I suppose.

Yes!

[China]

Just on a side note if that is designed to run on Natural Gas you will almost certainly need to to change the injector/s to run LPG

[abrogard]

No, that's all covered. Great big red notice underneath the thing saying it is for LPG only.