thanks. what does that mean?
What he's suggesting is one would stick an end mill cutter into a drill press, and then slide the material to be cut/machined underneath, much like one does with wood, using a router.
What a router does for wood, a milling machine does for metal.
However, having tried this, an end mill (cutter) is missing one key ingredient for use in a drill press - a point. Without the point as drill bits have, the end mill will "walk" at least slightly, making for a not-so-round hole and probably damage to the end mill itself.
Drill presses aren't designed to withstand much lateral force against the side of the drill bits, which is why they need to be razor sharp for clean drilling.
A milling machine on the other hand, are much more rigid and uses much larger, higher tolerance bearings, to specifically allow such forces.
This is why one can pass a cast iron cylinder head through an end mill, and "deck" the head flat within less than 0.001" without a problem. Drill presses are $99 for a reason