how they make it?

the recent "how it's made" post and 4140 post reminded me, what i'd REALLY
like to see is how they draw 4140 tubing. i've seen cross sectional views
of the machinery... and read about the process, but would really like to see
it in person, and if not in person at least on video. thing that puzzles me
is, how or why does the tube not thin off center, why does the tube never(?)
thin, thinner on one side and thicker on the other, and if it does how can
they detect it in the middle of a 20' long tube. i realize they have a
mandrel inside the tube, but i'm imagining it's got to be relatively long,
and therefore not rigid enough to resist any tendency of the tube to thin
out more on one side than the other. also, 4140 is DAMN hard stuff, there
must be TREMENDOUS pressures when they're drawing it. wonder how many
break. maybe that's why it's so expensive?
another thing. once a while ago a guy i know said "i wonder how they make
aluminum cans?!" since then i've seen episodes on tv about it and there's
even a guy i know who services can making machinery and he had in his house
a series of in-process examples, was pretty cool. what i said to this old
guy i know (who was wondering about the aluminum cans) "*I* wonder how they
make oxygen cylinders!" that must be some hairy incredible process, making
oxy cylinders, i mean, making something that you've got to draw THAT deep
and is guaranteed to hold all that pressure. and last that long. i had a
oxy cylinder that had lots of hydro test stamps on it, i think the first was
"23". it blows my mind that that tank has been around since (before!) 1923
and still tested good in the late 90's. would like to see that process on
"how it's made", how they draw oxygen cylinders.
b.w.