Drilling Sheet Metal

Sheet metals present a special challenge for drilling. The best way to drill in sheet metal is not to drill at all, but the use a punch. A sheet metal punch is basically a round shear. It pushes the part you want removed into a sharp edged hole of the same size and shape, cleanly shearing the hole. A couple of examples are shown below, a Whitney punch and a chassis punch. With a chassis punch, you need to start with a smaller hole for the bolt on the punch to go through.

Since it is not always practical to have all of the punches you need, we will talk here about drilling with a regular twist drill, which is tricky, and can be dangerous.

Step Drills

On way to drill sheet metal with with a special drill called a "step drill" or a "uni-bit." These are single flute drills specifically designed for cutting sheet metal by starting with a small hole and progressively enlarging it to your final desired size. This kind of drills does not pull the drill into the metal, but relies on you to push into the metal to the desired depth/diameter.