40 years of prying knockouts later, I have been frustrated every now and then, but accept concentric ko's as a part of the scenery. I have a nice set of Enerpac ko cutters that have 4 points and the liberal oiling of punch and dies keep the cutters sharp and allow the occassional custom located hole to be made without dragging parts of the adjacent concentric ko into the new hole (most of the time...).
Total agreement with iwire, if you don't own something as basic to the trade as a set of KO cutters, you have no business installing gear. A similar comment was made several days ago concerning the individual needing help calculating voltage drop on a 1600 Amp feeder, if you are clueless as to Conductor Properties and Ohm's Law, one has no bidness attempting to do work at that level. ...let's see here...did I put yellow or was it orange tape on the other end of this here wire...
