Boring head with a set of boring bars.
http://ttv.mit.edu/tags/331-to/video...machine-shop-7
A boring head is about $60 and a set of bars is $20 or so.
This is usually used on a mill, but can also be used on a drill press. With this, you could use just one piece of aluminum since you can control the dept of the hole. This is what I plan on using.