the trick to 'drill through any of the replacement front sight blades is to drill into the existing hole of the sight body, from BOTH sides, one side at a time, just a little bit, on each side ,so the hole meets in the middle of the blade................trust me , this does work,( unless you happen to be 'cross-eyed'......) 8)
and yes, you should have SOME concept of "square and perpendicular...." holding a drill motor, steady, helps too.
OR , place the sight blade and mark the hole on BOTH sides of the blade, then remove it and use a drill press, the spindle (quill) USUALLY is perpendicular to the 'flat' bed (table) :roll: