"Jeff Wisnia" wrote in message
...
Regular NPT pipe threads cut to spec have a built in "spiral leak path"
along
the crests of the threads, and won't seal under normal torquing unless
some
sort of sealant, pipe dope or tape, is employed. A glance at the thread
form
diagrams in Machinery's Handbook will confirm that.

Ah yes, that's true. I wonder how dopey scale is...
I doubt aluminum would get very far up the spiral, of course. And even if
it made two turns, it still has a ways to go.

The "dryseal" threads are made with a thread form which seals tight
through
minor deformation of the metal parts. They are usually found on brass
parts to
enable that to happen easily.

Would that be the brass 1/4" MPT fittings I use on my propane?

Tim

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