I'm interested in building a CNC machine, and would like to construct it mostly out of 1/2" aluminum plate, thus eliminating the need for welding.

I've heard people cut this stuff on their table saws, with circular saws (with a carbide blade), and band saws.

Since I own none of these tools, and cutting it with my jig-saw just isn't cutting it (excuse the pun), what would be recommended as the best, affordable tool for cutting aluminum, and possibly other metals.

I'm leaning heavily towards a horizontal band saw. That's what my Dad had in his shop, and I recall sticking a chunk of metal in there, tilting it down, and walking away while it did all the work.

Which tool will give the cleanest cut? How many passes are needed with the circular saws? What do you guys use?

Cleanest cut - Cold Saw, Power Hacksaw, Bandsaw
Fastest - Circular saws with carbide blades

What blades are you using in your jigsaw? How thick is the metal you're cutting. It could be that something as simple as choosing a different blade for your jigsaw will dramatically speed up the process.

Well, the jig-saw cut dreadfully slow using a fine-toothed metal blade, but the bigger problem was that if I tried to follow a square clamped to the metal, the bottom of the blade would drift inwards, while the top tried to follow the guide. The result was a progresssivly worse angle.

When I tried running the jigsaw by hand, I could correct it, but that cause a wavey cut, and a very rough finish.

If just making straight cuts, go with a circular saw. It's the fastest and least expensive.

If your using a circular saw with carbide tips, positive rake works well.