Thread: Stag Jointing paste - What am I doing wrong??

Originally Posted by .RC.

The male threads should be tapered.. That is what makes the seal...

I have never had much luck with that stag stuff...

Ha ha me neither as a fitter using stag paste and hemp it always ended in a nightmare. I could of kissed the chap that invented Teflon tape

A friend is a plumber he told me a story about Stag, you may find it amusing.

He was called to install a gas heater in an upmarket side of the city, newly renovated with white carpet, he arrived late in the afternoon so lady of the house left him to it while she dashed out in her Merc to get some groceries for dinner.

He always used flared copper pipe with a touch of Stag to unsure gas tight joints, pipe was bent into shape and ends were flared ready for the Stag to be applied from the tube, where was that other spanner ? he thought I'm sure I had it in the tool bag, looking all over he couldn't find it so out to the ute to retrieve it. Returning to the house via the the front door he was greeted by pristine white carpet and perfect red foot prints leading to the lounge where he was working, in searching for the spanner he had stepped on the tube of Stag squeezing most of it onto the carpet, then very neatly stepped into it and tracked it out to the front door.

Originally Posted by achjimmy

I could of kissed the chap that invented Teflon tape

that would be me then...lol

Originally Posted by Chief Tiff

As Usee says you should be using tapered threads.

You do realize that main water pressure runs in the region of 140 psi for most households, and can go as high as 160 psi if you're at the bottom of a hill coming off of a main feeder pipe.

So it is actually higher pressure than most air comp systems.

No tapered threads used.

Thread sealer (tape or liquid) works against the thread faces and seals the coupling.

In fact water pipe and threads are often used on farm equipment (speaking from experience) for much higher pressures in hydraulic applications.

Tapered threads are the ideal, particularly where thread sealer could dissolve or contaminate, but plain threads can do the same job if made correctly.

Cheers

Rob

Originally Posted by nearnexus

You do realize that main water pressure runs in the region of 140 psi for most households, and can go as high as 160 psi if you're at the bottom of a hill coming off of a main feeder pipe.

So it is actually higher pressure than most air comp systems.

No tapered threads used.


Rob

Are you sure about this Rob?

Originally Posted by Techo1

Are you sure about this Rob?

Yes.

Put a pressure gauge on your mains water pipe supply and read it off.

Up the farm we get 160 psi in some paddocks and run pressure reducers to prevent float valve blow out.

Water pressure is much higher than most people realize.

That's why when a major pipe bursts it makes a good fountain.

Thread cutters (as used by every plumber) DO NOT make tapered threads. Check out water pipe fittings in your hardware store next time - not tapered.

I have seen some plastic fittings with slightly tapered threads, but steel general run of the mill fittings are parallel thread.

Cheers

Rob

Yes Rob, I know that mains water pressure can be over 100psi, what I was questioning was your statement about
non tapered threads.(see Bold Text) Every water pipe joint that I have ever seen, or cut myself, has at least one element of the joint tapered, either the internal fitting or the end of the pipe or fitting or both.

Hi Rob
My thread cutters (that plumbers use) cut tapered threads.

Phil

Originally Posted by Steamwhisperer

Hi Rob
My thread cutters (that plumbers use) cut tapered threads.

Phil

The thread dies are tapered for feed in as per any other die, but if you cut past an inch or so it will produce a parallel thread.

Also check out the internal thread on a tube or T connector (galv steel) and the thread will be parallel.

In fairness, most male pipe threads are only cut for the first inch or so and that feed in taper does help seal the joint, but the female section will always be a parallel thread.

However, if you buy a length of threaded male pipe to cut up for internal joiners, it will be a length of parallel thread.


Rob

Originally Posted by nearnexus

The thread dies are tapered for feed in as per any other die, but if you cut past an inch or so it will produce a parallel thread.


Rob

That's not how BSPT dies are designed to be used Rob. There are BSPF Dies for that.

Originally Posted by familyguy

He always used flared copper pipe with a touch of Stag to unsure gas tight joints...

Well he's a naughty boy then. AS5601 forbids the use of thread sealant on a flared joint for gas.

Originally Posted by nearnexus

The thread dies are tapered for feed in as per any other die, but if you cut past an inch or so it will produce a parallel thread.

Also check out the internal thread on a tube or T connector (galv steel) and the thread will be parallel.

In fairness, most male pipe threads are only cut for the first inch or so and that feed in taper does help seal the joint, but the female section will always be a parallel thread.

However, if you buy a length of threaded male pipe to cut up for internal joiners, it will be a length of parallel thread.


Rob

Hi Rob
the BSPT dies as Techo says are tapered to produce a tapered thread at 1:16 taper not including the lead in taper that every die has.
I have just completed a job with sockets and valves and not only are they marked BSPT but the threads are actually tapered as well.
I can't see why a thread would need to be longer than an inch with most of the stuff that we are likely to do at home as it only exceeds that length, (according to the standards), when you cut a 2 1/2" NB thread and larger.
Techo is also correct in talking about BSPF threads but these are structural threads and BSPP is the parallel thread for pressure pipe.
The fittings I used, ie sockets and valves, were actually stamped BSPT and by golly when I fitted them together, they surely were.
The 'length of threaded pipe' you refer to are like allthread and are normally used in bulkhead situations.

Phil

BSPF and BSPP are just two designations for the same thread, there are others as well.

Originally Posted by Techo1

BSPF and BSPP are just two designations for the same thread, there are others as well.

BSPM British Standard Mechanical Thread. Same animal, different day.

You blokes need to get up to speed with Metric G & Rc threads.

Don't shoot me, I'm only the piano player, Thank you Reginald Dwight.