1000 series aluminum is gooy to machine & sticks to tools badly. Electrical aluminum is like that. Some of the aircraft grades like 6061 & 7075 are much better to machine & finish well. I'm currently making my first set of homemade blocks out of some 6061 T6. You can check back on my thread in a week or two to see how that worked out for me.
http://castboolits.gunloads.com/showthread.php?t=45741
6061 is a little tougher than the softer grades of aluminum & produces chips that are easier to handle. You do still need a little cutting lube, but it's not bad to work with at all. It cuts best with sharp tools that have a very positive clearance angle on them. Heavy feed rates work best for roughing. Slow feed rates & high spindle speeds are best for finishing.
If you are going to machine brass, keep the clearance angles on your tools shallow. Copper alloys love to suck a tool in & destroy the part if you let them. Other than that, free machining brass is generally pretty nice to cut. Be aware of the heat treat you get with brass. Half hard brass is more than a little tough. Full hard brass is just what it sounds like.
McMaster Carr is a good place to get small quantities of aluminum, brass or steel. They may even have low carbon ground steel stock in the size that you are looking for. I think that they may even have Starret brand. That stuff is first class precision material.