Aluminum is a string mess usually, using a HSS bit I assume?? You could try and rig up a chip breaker top piece kinda like old wood planes have. it might help but HSS and aluminum mostly spells stringy mess. Make your self a chipgaurd is the easiest solution.
Have seen some like this, have seen others made from a magbase with locline (hose and a piece of lexan) others that just had apiece of lexan bolted to the back of the tool post or compound table.