If you imagine cutting out rectangles from sheet metal, you can completely tile the plane. Punching out circles, you'll use a maximum of roughly 91%. So I imagi

If you imagine cutting out rectangles from sheet metal, you can completely tile the plane. Punching out circles, you'll use a maximum of roughly 91%. So I imagine the more of your material you use for the sides, the less scraps you'll end up with. I'm sure the problem is a lot more complicated than this though, with deburring, corrugation and whatnot.