Would it be worthwhile to save all the chips,swarf from a project using the same type of aluminimum to smelt it and re-cast other parts? Obviously coolant would have to be washed away but milling all that metal away seems to me to be a big waste unless you could reuse it for other projects, test pieces etc.

Cheers,
Tom

Yes you can. In highschool we did some aluminum casting, and used everything from swarf to pop cans to old pistons. When you melt everything most of the crap comes to the top (no big worry about oil or coolant) and you skim it off.

Just out of curiosity, would a casting from swarf have the same machining properties as the original piece? Just wondering if the melting/casting process would change the metals characteristics.

Throw away the swarf.
It will only create lots of slag in melting. That's a waste of expensive heat and volume in your crucible. Also throw the poop cans where they belong, that's not good aluminum for casting. Pistons on the other hand is good if you can get them cleaned first. Heat throroughly before putting it in the melt though. There are lots of crevices that can hold oil or moisture and create an explosion.
If the material is clean and in reaonably large chunks, you will get a casting with close to the original characteristics. You *must* degas, or it will be brittle and with tiny gas pores in it. (There are now less harmful degassers than Hexachlorothane.)
Do not let the melt come in contact with iron, then it will generally not be useable for anything but plaques and figures that will not be machined.