I have gotten some PM's in the past where people have made incorrect or want to change the size hole they made in a drum. If you have ever tried to drill a large hole in thin metal you know that it does not make a clean round hole. It is even worse on a curved surface like a drum. You can get a bigger unibit which are either expensive or don't work very well or last. If you use a tool called a "Chassis punch or Knockout punch" it makes life very easy. A industrial quality punch will cost @$40 apiece but Harbor Freight sell a set that will work on drums for <$20. Here is a link and a link to a You Tube demo. The pilot hole does not have to be only slightly bigger as described. That is how they are designed but you can go bigger if you pay attention to centering and make sure it is shearing the metal as you tighten.