[DougC]

Is both the male & female threads tapered, or just the male? I cannot
see from the examples I have on hand if it is both or not. Wikipedia
seems to indicate both are.

I could cut external tapered threads on the lathe (I think,,, never done
that yet) but don't know how I'd do internal ones since the lathe has no
taper attachment.

Relating to the aluminum radiator building--I have to relocate the
coolant temperature sensor, which uses a 3/8"-18 pipe thread. It screws
into the top of the thermostat housing.... so what I need is a nipple
for 1/2" ID hose that screws into the thermostat housing, and then I
need to make a "T" fitting that the temp sensor will screw into, along
with two 1/2" hose nipples.

I had assumed there would be taps & dies for this. I have found many
sources for cheap dies (pipe threading kits) but no taps yet, and the
dies are "long" because they are for threading pipe.... Is there any
'normal' taps & dies sold for this, at a /relatively/ cheap price? I
just need the one 3/8"-18 size, internal & external.