Ignoramus11107 wrote:

I had a chance to thread some 1/2 NPT pipes. The threader worked,
however, the vise (Harbor Freight 4" vise) could not hold the pipe
well, so the pipe would slip. I tightened the vise rather well. This
is a vise with no special pipe holding provisions.

My question is, is the vise somenow not as good as it should be, or
was it simply a wrong tool for the job? Do vises with pipe "slots"
hold round objects better?

i

A pipe vice is what you need. What you can do is to secure the pipe in
the vice you have and put a pipe wrench on it while you thread the other
end. An old three jaw chuck would hold the pipe too.

John