Don't try milling with your drill press unless your drill press chuck is positively retained in the spindle by something other than just a tapered arbor. Without positive retention, the side loads caused by milling are very likely to cause the chuck to fall out and bounce all over the place, aka the "hand grenade" effect. My 40 year old Craftsman drill press has a threaded collar on the chuck which screws over male threads on the spindle to keep it in. And if presses I'll confess that I've done a few light milling jobs on it, but only on wood and aluminum.
Also, drill press quill bearings are not sized to take the side loads created by milling, nor are the quills.
Years ago I saw an illustration of a drill press "milling adaptor". It looked like a split collar which clamped onto the press column which had an adjustable length thrust arm projecting from it. The arm sported what looked like a couple of "roller skate wheels" at its end, rotating in a horizontal plane.. The adaptor was set up so the body of the chuck rode in the valley between the two wheels. Milling operations had to be set up so the side loads on the chuck were supported by the adaptor's wheels. I suppose that meant the direction of cut was in line with the suport arm, but maybe you had to give it a little "windage" to account for side loads caused by the rotating milling cutter.
It couldn't have been terribly effective, as I've never noticed one advertised as a drill press accessory. Anybody else ever run into an adaptor like I described above?
Good luck,
Jeff