On Sun, 25 Sep 2011 11:54:10 -0700 (PDT), Deodiaus wrote:

What I really want is a "concave router" bit? Is that the name?
Basically, something that looks like an cave with teeth. I am sure
that some Dutch craftman must have a dozen of them if I know where to
look.

A "round-over bit" bit will cut a quarter-round profile (two passes gets a
half-cylinder).

Basically, something to attach to the end of my drill so that I can
round off the ends of the banister.

There are bits intended for this, but you're nuts if you think you're going to
do this with a drill.

My banister cross section is an ellipse, about 1 inch high and 2
inches long.

There are all sorts of router and shaper bits around to do this sort of thing,
but again, forget the drill. It's not going to work and you're likely to hurt
yourself.