I've always wondered about doing this as well. I have a ton of antler sheds, and could make a whole bunch of these if I ever had the time or inclination to do so. My thought would be to remove the centering bit from the hole saw, clamp the antler in my drill press, and then cut. Each cylinder would produce two buttons, once the center portion is removed. I'd make a jig to hold the buttons for drilling the thread holes in the drill press as well.