Npt threads

[Triumphman]

Is there such thing as npt parallel and npt taper thread? Like with bsp?

How do you put a taper thread on a pipe without taper screw cutting?

 

[Paul99]

No idea about parallel npt but curious as to why it would be needed instead of standard BSP? as for cutting tapered threads we have a couple of these: http://www.ebay.co.uk/itm/PIPE-THRE...DIY_Materials_Plumbing_MJ&hash=item1c3d4737eb that do the job on a range of sizes. Only used them maybe half a dozen times in the last 10 years but their worth their weight in gold when you come across an old galvanized water pipe that needs repairing quickly / cheaply.

 

[Rocketman]

You can also mix BSP and NPT quite successfully. Maybe in very high pressure circumstances it may not be the best idea. In mould making sometimes you buy cooling items with NPT thread and all that the toolmaker ever does to fit them is tap BSP and use PTFE tape like normal.

 

[Triumphman]

Ok
Do those pipe threaders put a taper thread on then?
Do they cut a range of tpi and sizes?

 

[Paul99]

Ok
Do those pipe threaders put a taper thread on then?
Do they cut a range of tpi and sizes?

I've just been out the shed to check ours... Both have the words "BSP" and "Tapered" stamped / engraved into the casting and from experience yes they cut a tapered thread as you wind it on. The thread shape and pitch is set and would be determined by whatever die cutters are installed - likely back in the day you could get different cutters to suit other pitches /and tapered / non tapered too - god knows how easy they would be to get hold of now though. The two we have are adjustable to suit a range of pipe sizes one goes from 1/8" to 1 3/4" (looks very close to the one in the link above) and the other 1/4" to 2 3/4" you just set the pipe size according to the marks on the cutter and away you go.

 

[Stueeee]

The Parallel version of NPT is called NPS (National Pipe Straight) used on USA made stuff in the same way as BSPF (British Standard Pipe Fitting) confusingly sometimes called BSPP (the last P being parallel) is used on Brit made stuff.

 

[waldershelf]

You can also mix BSP and NPT quite successfully. Maybe in very high pressure circumstances it may not be the best idea. In mould making sometimes you buy cooling items with NPT thread and all that the toolmaker ever does to fit them is tap BSP and use PTFE tape like normal.

Only in certain sizes, when the TPI matches. The thread pattern is near enough for most applications.