On 2008-01-14, Stealth Pilot wrote:
On Mon, 14 Jan 2008 05:56:18 +1300, Tom
wrote:

Stealth Pilot wrote:

[ ... ]

a 1/4 x 18 straight thread is NPSF (straight) DRYSEAL ...whatever that
means in english. it is a pipe thread.

in a taper that thread would be NPTF (taper) DRYSEAL.


Stealth Pilot

I hope you read you pilot notes with greater concentration than you did the
original post? :-)

[ ... ]

why what's the problem? I read the details from my mullins thread wall
chart. it lists the 18 pitch threads exactly as quoted.

Out of curiosity -- what does the mullins thread wall chart say
is the OD of the thread. IIRC, the original question said that the
actual measured OD was 1/4", while any pipe thread would normally be
named for something closer to the bore size, thus requiring a much
larger diameter for the threaded part.

the post answers the last two sentences of the question.
a. what's it used for? - pipe thread.

Not clear -- until you can tell us that your chart shows the OD
as 1/4". It could easily be some other thread with the same pitch, but
a smaller OD, for a different function.

b. his suspicion that it was a mistake is probably wrong since there
is a listed application for the thread size.

Again -- are you sure about the OD?

Enjoy,
DoN.

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