^^^There you go. I use dremel grinding bits of various sorts, whatever I can find/grab at the moment. I don't worry about how neat or consistent it is. Just open them up. Keep in mind you don't really need thick walled pillars at this point. What you need is enough material to prevent the screws from compressing the stock material when tightened. Chances are, if they are paper thin, but surrounded by epoxy/bedding material, and the screw head is stopping against it without crushing the pillar or the epoxy, and the shank is not touching the pillar, then they are doing their job.