making ball nuts

These things are so !@#$%^! expensive; has anyone ever made their
own. Isn't just a matter of cutting an internal thread with a half-
round form tool, e.g. a round carbide insert or hardened piece of
drill rod?

I don't yet fully understand all the details of ball recirculation,
but it looks like drilling some holes and silver soldering some
tubes. Preloading means making two of 'em and sourcing a spring,
right.

So, group, what obvious factor am I missing?

Thanks in advance.

--Jack W.