Those rivets are stainless steel if I'm not mistaken. A drill press is the best thing, unless you have a way to hold the drill real steady. Although I know a trick to help if you really want to use the drill. Since the rivets are rounded and slightly above the the surface of the scales. You can slowly grind a flat area with the grinder. That way the drill bit don't wander around. Also you will probably need several drill bits as stainless is a real pain the smurf to drill.