Run a Daewoo puma 250. using kenametal fixed index drills to drill holes. drills fine most of time but sometimes I think i'm not exactly drilling on center. leaves a nipple inside of hole. changing drill inserts often especially the inboard tool. what can be done to know that i'm exactly on center?? usually happens with smaller diameter holes such as .500 .625 .750 all the way to 1.0 the 1 inch diameter holes and up to 2.125 holes seem to drill alot better. ????