When trying to drill holes in chassis' I use a transfer punch to start. The layout is critical when using countersunk screws like those needed in this IEC plug. The transfer punch leaves a shallow depression, but not really enough to go hogwild with a hand drill. So, I start with a 1/16" bit in a pin vise and deepen the starter hole a bit more to lessen the "bit walkin" that would really screw up this nice chassis....