|End mill holder with my "reverse drawbar" arrangement|
A common question on machining forums across the internet is about making a drill press into a milling machine. The consensus answer is "don't try it, don't even ask".
From what I can see, the most common reason not to do it is that there's no drawbar and the side loads put on the endmill do not allow whatever taper is used on the drill press to hold well enough. Eventually the chuck or whatever holder you have will fly out of the spindle.
The second most common reason I see is that the drill press is not beefy enough to provide a stable platform.
Read on for my version of the infamous "drill press mill".