The best way I found (after MUCH) trial and error was to use a bit that is just slightly larger than the littlr center "dimple" of the rivet. Make a pilot hole to about the bottom of that dimple, then use a bit that is about half a mm smaller in diameter than the rivet mushroom diameter (it's 9/64 in the US, but not… » 8/18/14 6:04pm Monday 6:04pm