How to Drill a Hole in Sheet Metal
Preparing to Drill Through Metal
Before you can go about drilling holes in your sheet metal, you need to do some layout work, like finding the exact centres of all of the holes you need to cut. It can be very beneficial to use a compass to draw, or even better, scribe the exact hole size you need to cut out once you’ve found the centres. This will give you a visual guide and help you cut the hole in the correct location. Then use a centre punch and hammer to strike the exact hole location.
Securing and Protecting Your Sheet Metal
If your sheet metal is easily scratched or scuffed, consider using a masking material on the sheet’s front and back to prevent damage. Masking materials are strongly recommended when you need to drill a hole in a piece of sheet metal that has already been polished. Before you can begin cutting your holes, you’ll need some clamps to hold your sheet metal in place. Never use your hands to hold the sheet metal while you’re making holes. A drill bit can get caught in the sheet metal and cause it to rotate rapidly. Ensuring your clamps are tight will prevent the material from moving during the drilling, thus reducing the risk of damage and injury.
Methods for Drilling Through Metal
Depending on the size of the hole required and the thickness of the material, you have various methods to choose from to best suit your needs.
If you’re working with thin sheet metal, a portable hand-punch is an easy, quick, and clean method to make holes. Leaving no sharp edges behind makes the hand-punch ideal for projects where you don’t want to deal with deburring. Thicker materials require a bench-mounted punch or knockout punch to provide enough force to pierce through the sheet metal.
Sometimes a hand-punch just won’t cut it, and you need to upgrade to a knockout punch. Knockout-punches are easy to use and can handle larger holes that hand-punches can’t. Using a three-part mechanism, a knockout-punch uses sheer force to cut through the sheet metal. Unlike a hand-punch, the use of a knockout-punch will require some deburring.
Traditional Twist Drill Bit for Metal
Twist metal drill bits are an excellent option for making small holes. Like other materials, you’ll start by drilling a small pilot hole in the sheet metal and gradually increase the drill bit size until you reach the required hole size. This method is effective but not for large diameter holes as gradually increasing the drill size will be time-consuming.
Step Drill Bit
A step drill bit is less time-consuming due to its ability to cut multiple sizes in a single use. Like twist drill bits, step drill bits do require a pilot hole to be drilled first. However, some self-starting drill bits do not require a pilot hole to be drilled first, thus making it an even more desirable option if time is of the essence.
However, a hole saw will be your best bet if you need to cut a large diameter hole. Instead of drilling into the sheet metal, a hole saw will cut the hole at its exact size like a sawtoothed cookie cutter. Depending on the thickness of your sheet metal, cutting fluid can aid in cutting and prolong the lifespan of the hole saw. If you are using a handheld drill on a clamped piece of sheet metal, make sure you brace yourself to prevent any kickback from the drill. In addition, a hole saw will leave sharp edges behind that you will need to deburr. Safety should be your number one priority no matter which method you decide to use; always wear proper PPE like safety glasses and work gloves when operating drills and hole saws.