Hello! I have 144 pieces of 1" ID 3/16" wall aluminum tube I have to make "slots" in.... kind of like 1/2 of an oval. I can't figure a way to make the oval, and what to use as a starting point. Everything else I do has a corner to reference as a start point. I've attached a rough drawing of the part. I'll be using a 1/4" Dia. single flute end mill.