In article , Ned Simmons
says...

As far as finding a spec, I expect you're right, and I said
as much in a post to the OP back on 10/2. My objection is
to the several (unsubstantiated IMO) assertions that pipe
threads are unsuitable for carrying axial loads.

Not that they can't, but rather they are supremely
unsuited to it. The sharp V thread form provides
on problem, and the fact that NPT threads are
invariably die-cut is another.

Die cut threads are rougher and this roughness
translates into microscopic tears in the
thread - surface defects that provide stress
concentrations. That and the sharp V form can
weaken the thread by large factors compared
with properly rolled threads.

This is why no pipe manufacturer would ever suggest
his fittings be used for axial loads, and would never
supply a spec for that purpose.

Sure for a railing or something it would work fine,
and your own numbers suggest that his lift will
not fail unless subjected to a shock loading of
five or ten gs.

Jim

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