Soon to start the process of cutting out my cnc machine. My question is, do I pre peck the drill holes with a center end mill? Cutting 3 and 6mm aluminium sheet. The reason I ask is there will be four differnt sized holes (3mm, 4.2mm, 5mm and 6mm)in the job and I plan to use a regular jobber drill bit to drill out most of the holes. Or is it possible to just drill/mill all the holes using the 3mm 2flute hss center end mill? Excuse my terminology, I am still a nube.