Brian,
You are correct, 540 rpm is too fast for drilling a 7/8" hole in steel with a standard HSS (high speed steel) drill bit.
Years ago, when I bought my drill press, I was looking for one that would go as slow as 300 rpms or less. I ended up buying an inexpensive model made overseas (Taiwan) that has 16 speeds ranging from 215 to 3250 rpm. I have had this drill press for more than 20 years, and it works fine. I have drilled holes up to 1" in mild steel without any problems. As mentioned above, I use cutting oil, when drilling steel. Mine is a 3 pulley model. That is most likely what you will need to have, to go that slow without having to use a very large pulley on one side and a very small one on the other.
Also, as mentioned above, it is not so much the thickness of the material that matters, but the type of material, type of drill bit (high speed, carbide, etc.), and the hole diameter that you are drilling.
If I were you, I would look for another drill press. Or do your heavy drilling on someone elses.
Good luck
John
