Mag drills, or magnetic base drills, are great for core drilling holes in heavy steel. The electromagnetic base holds these tools in a fixed position while the cutter is fed into the material just like a standard drill press. The annular cutters used with mag drills are hollow inside which drastically cuts down on the amount of material being removed and the horsepower necessary to drill larger holes. Considerations when choosing a mag drill are maximum hole diameter needed, thickness of material being drilled, and space restrictions (i.e. low profile for truck frame drilling).