wrote:
Greetings, folks...

Let me preface this by saying I'm a complete and utter novice when it
comes to this art -- to the point where this question is actually
asking what tool I need.

Using some standard brass 3/4" pipe, I want to resize portions of it
down to 1/2", similar to this shape:

http://devnull.dtcc.edu/gfx/shape.jpg

Can this be done with, say, a mini-lathe? I was under the impression
that a lathe was strictly for shaving down an item, but I've had
someone else suggest it can be used to actually change the diamater in
this respect.

If it is possible are there any structural disadvantages?

Thanks!
Rob

It can be done on just about any lathe regardless of size. If the lathe
does not have a taper attachment then typically the compound rest is set
at the taper angle and this is used to turn the taper portion.