o prevent the drill chuck from ramming the finished sink as it breaks through. use a magnet to pick up the cast shavings and do not allow them to get wet or rust into the white sink. post some photos. now if the hole required is a standard 1.25''- 1.375'', then you better get someone who owns theses bits and knows how to do it. it is not the breaking of the sink to worry about, it is the chipping of