On 2/9/2012 12:52 PM, whit3rd wrote:
Yes, of course the usual pipe taps are tapered.
You will want to use Al parts, because Cu is
a major corrosion issue -- maybe galvanized
is OK, though.

If you bore and straight-thread on the lathe, the
final machining is just a quick touchup with the
tap. Just look for NPT taps, stands for
National Pipe Thread.

Well I did end up just ordering some aluminum nipples and a "T" fitting
from McMaster. The remaining question was how to cut internal tapered
threads on a lathe that didn't have a taper attachment.

I saw the NPT taps at Enco, $28 for a 3/8"... Enco was offline at that
moment...

I noticed that the temperature sensor was brass, and it screwed into an
aluminum thermostat housing--and there appears to be some brown
corrosion in the aluminum thermostat housing threads. I couldn't tell
from briefly looking if that was the aluminum corroding or not. I had
not seen this connection leak before, so the rust I saw may have been
free-floating rust from the iron engine block (this is why I built the
magnetic trap in the new radiator tanks).


I know that the local hardware store sells brass and steel/zinc plumbing
fixtures, but I wanted at least one aluminum nipple to screw into the
remaining thermostat housing threads. ...As for the remaining
components, I got them in aluminum also since I had to mail-order the
one aluminum nipple from McMaster, and the thermostat sensor can be
grounded directly off its own body so there will be no current flowing
through the brass/aluminum there connection at all. This may not
eliminate corrosion in the sensor threads, but should drastically
eliminate it.