what to use to cut cast aluminum

How straight do you need the cut can depend on how you cut it. Also, what tools do you have at your disposal? I am not sure how thick the wall of piece you are cutting is either.

If you have a chop saw or cold saw either those would be great. Also, a band saw for metal, vertical or horizontal would be great. If not, you could use a recip saw, but you need to make sure you set it up so it cuts straight. If you are strapped for money for tools, you could use a good ole fashioned hack saw. With either the recip saw or the hack saw, you might need to clean out the blades every so often. Alum can tend to gum up the blade. Just take some compressed air or, rag, or paint brush to clean the blade. If you want a precise straight cut, just make up a jig for it. such as using wood to block your piece with.

Pretty much anything that cuts stell or plastic will cut aluminum, it just depends on how precise you want it and how do you want the cut.

Good luck

got a chop saw? that would give the cleanest cut at home.