Taper Threads in Boilers

Whilst looking through the stock of a tool store in Turin I came across a big range of obsolete imperial taper thread dies. They are all brand new and in the original packaging.
They seem to be to a BS standard and they are up to about 3" in diameter. Apparently they were used for industrial steam pipe fitting until there were no further contracts.
Could these be of use in tapping out holes for boiler fittings or for pipe runs? What types of threads are used in full size heritage boilers?
All my boilers up to 4" scale use the standard parallel type so I have no knowledge of the thread data, though the thread angle looks to be less that the std 60 deg metric. If anyone thinks they could be of use let me know and I can put you in touch with the supplier. As they have been sat on his shelves for years he would be glad to get rid of them otherwise they will get weighed in.

 

BSP taper threads (designated BSPT) are still in widespread use, not only in the UK but throughout Europe and beyond. They are used for pressure tight joints on steel pipework. If you have a screw thread on steel pipework it will invariably be of this type. I would doubt that you would class them as obsolete. They do have some use on steam locos (eg vac pipework or other steel pipework) but are not used on copper pipework and very rarely used on locomotive boilers, although fittings on industrial package boilers often have them.

 

NPT is still widely used in the USA, it being of US origin..

 

Thanks for the information. The chap at the warehouse says he hasn't sold any in 15 years so is looking to get rid of them to make space. I'll probably squirrel away a set just in case.