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From: "Gary Casey" <glcasey@adelphia.net>
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Subject: Re: Pre-Oiler... Infinity costs and plumbing...
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<<Then the next bit of fun is finding the fittings to go into the Infinity
pump.
Pumps for some arcane reason come with straight (not tapered) pipe
threads.>>

Actually, there is a reason for that.  Most, or at least many, internal pipe
threads in automotive applications will be NPS rather than NPT.  The reason
is that if you put an elbow or some other device on it that needs to be at a
certain angle the straight thread gives more flexibility in angle - you can
usually get another half-turn if you need it.  Also straight threads cost
less as there is no exact tap penetration requirement.  Next time you're in
a hardware store take a look at a pipe coupling, which will usually have a
straight thread.  Nothing wrong with them - they seal just as well as
tapered threads (NPS is only for internal threads, by the way).  There is
reason to believe that they seal better than tapered threads because there
is more local thread deformation.

There's your bit of trivia for the day.

Gary Casey