[Dixie Gunsmithing]

About the most you can mill on a drill press is wood, plastic, and soft aluminum. The chuck will slip on it's taper, which is most likely a Jacobs on that end. Either that, or the Morse taper may slip, but most of the time, it's the Jacobs, as it has a sharper angle. Most drill chucks aren't precisely centered either.

Another problem is the quill size, and the bearings. It is made to drill all right, but general drilling isn't that accurate. To keep it from vibrating, you need the quill all the way up, and locked.

Last, wood, and plastic require a fast cutter speed, so one would be better off using a router. That leaves soft aluminum, but I doubt you will get very accurate cuts on it, as there's generally way more runout in a drill press, and way more vibration.

The above is considering smaller shop drill presses, not the larger industrial versions, which are meant for machine shop applications. The ones from Delta, and others are really too weak to mill with.