What is this single tap and die for?

Question

Hello all.The recent thread on taps and dies prompted me to look again at my (yet unused) all metric set (bought from Screwfix some time ago).To my surprise, I found the following:One single short length tap, and one die.They are marked "NPT 1/8 27". Now, I haven't the slightest idea what they are for.I'm not entirely surprised, as this set also contains a screwdriver, centre punch, thread gauge, and five stud extractors (of the l/h spiral variety).I'm guessing that they are probably used for "cleaning" damaged threads.But on what fittings?Answers will be gratefully received.Sylvain.

PeterK · Accepted Answer

Have a look at  = US National Pipe Thread1/8 = nominal size of pipe27 = threads per inchPeterK

Roger Mills · Answer

NPT is a pipe thread used in USA - similar to our BSP.

1/8" NPT is roughly the same size as 1/8" BSP (just under 10mm in diameter) but has 27 threads per inch compared with BSP's 28.

I have a feeling that things like engine oil pressure switches on cars had used to use NTP threads. I doubt whether they still do - more likely to be metric, these days.

Sylvain VAN DER WALDE · Answer

Thanks for both useful replies.Sylvain.

What is this single tap and die for?

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