I do same as Cobalt , put the shank horizontal in a vice and manually drill it, to mark the hole center I use a combination rule ( the ones with slide on attachments) and use the center finder one, mark 3 t0 5 lines ,if not round you can see the centre in between all the lines pop it, find a small spirit level and set you drill with a long bit horizontal and stick the level to the drill reading horizontal, this gives you a visual vertical positioning of of the drill, the horizontal position is by eye,