Trying to cut steel on Homemade Milling Machine

[KustomsbyKent]

Having been down this path before, I'll add my 2 cents worth.
I have tried using an x-y table on a drill press, and it just isn't stiff enough for any serious milling work, particularly in steel.
You will always be struggling with flex due to the column of the drill press that just isn't stiff enough, and will flex.
I have used small mill/drills, and while better than a drill press with x-y table, they still want to flex and move.
Before you stick further money into this setup, consider looking for a small vertical mill... even a well used and sloppy one will still be a much better platform, and will be worth putting money into. Depending on where you are, used mills can be quite easy to find, or not so easy. In South Dakota, they fairly scarce. My big mill came from PA, and was definitely worth the shipping hassle. I recently added a much newer/smaller mill, but paid much more for it, as it was a retired guy selling out. It has been very handy for the work I do on it.

An x-y table on a drill press is really only useful for drilling holes in accurate positions on small workpieces.