Hole Saw Cutters and Drill Bits made particularly for cutting metal so that you can turn your drip pan into a drain pan in the field.  Various sizes of cutters in this category allow you to cut the drain hole you require in the location that you desire.  Clean any holes around the edges with a sanding tool to knock off burrs or other debris that may affect drainage out of the pan. WATCH: How to Drill a Custom Drain Hole