As others stated, WD-40 is the problem. I use my used engine oil for cutting fluid. I use a flux brush to put a dab on the cutter before it touches metal, then as soon as the bit or cutter finishes the hole/cut, I dab a little more on. My drill bits and cutting tools last a lifetime because engine oil is one of the best fluids for machining. Not EPA approved, but cheap (free) and effective.
If you do go the water based cutting fluid route, the fish tank pump works great. I use that on another machine that uses water based lubricants.
As others stated, use a different lube for Aluminum, either store bought or the kerosene/atf homemade mix. Google other recipes for AL.