Npt thread

[Triumphman]

I've got a component that needs a new piece of copper steam pipe screwing into it. I believe the thread is either 1/4 or 3/8 npt (not measured it yet, but it's american so I'm sure it's npt)
The hole in the body is already tapped so I can't change that.
Working pressure is 150psi.
What's the best way to put an npt thread on a piece of copper pipe?

 

[Spark plug]

Is the pipe supposed to be threaded as it would need to be quite thick walled to take the thread. Dose it not need an olive and tube nut or other similar fitting

 

[Triumphman]

Hi
Yeah it's thick walled pipe

 

[MattF]

Use a die. Is the pipe actually around 1/4" diameter, (not sure if NPT is like BSP)? How long a length? Some tips for oxy-acetylene torches have that thread on them? Might be possible to use one of those if you only need a short length of pipe.

 

[normspanners]

npt and bsp is very close at that size so you would get away with bsp, but i have threaded copper by annealing it first, and also brass , by using a tapered steel fitting with slots cut in it with a hacksaw to form a die nut the steel is easily hard enough to thread annealed copper, as a 'one off'. But you must cut the clearance slots big enough for the swarf to go into to save it jamming up.

 

[Triumphman]

Had another look at this job.
The pipe I need to make has a thread on one end, which measures
9.5 o/d and is close to 28 tpi. (Not got guages handy, so measured a length and counted)

The other end has a union and nut, and the nut (which needs replacing) screws onto a thread which is 13.8 o/d and 24 tpi.

I expect the smaller one to be 1/8 bsp or npt. It's an American part.

But the bigger one, dos'nt seem to match either scheme?

 

[MattF]

It's definitely 24 and not 26 TPI?

 

[Triumphman]

Could be, I'll get some thread gauges and have a proper check

 

[MattF]

If my math is correct, (13.8mm should equal approx. 9/16"), and it is 26, then it's likely a 9/16" BSB. There is, however, a 9/16" 24TPI thread: http://www.tracytools.com/9-16-x-24-tpi

 

[Triumphman]

Right,
The pipe has an 1/8 npt thread on one end and a 1/4 npt flared end with Union nut.

The threaded end should be easy, just thread it with a die.
The other end I'm gonna require a 1/4 npt union nut.
I don't fancy making one really, internal screw cut blind to a shoulder and small, not fun.
Are there any good pipe fitting suppliers who do npt steam fittings? 150psi brass or bronze

 

[eil]

Try a refrigeration suppliers for a flared nut. (I think its 7/16 - 20 UNF )

 

[Triumphman]

Cheers everyone.
Think I've sorted the new pipe.
Final repair needed is a missing needle from a valve.
The thread on the spindle is 0.250 o/d and 22 tpi. Prob 60 degree as American.
Any ideas what this thread is? Might have to screw cut this, external thread so a bit easier.

This is technical for a mere boiler smith.