Drilling through stainless steel is not impossible, even though it may seem like it. Stainless steel's chromium content makes it more difficult to work with than carbon steel. Drill too slow or too fast, and it becomes work-hardened, making it even more difficult to drill through. The key is to find a happy medium between the drill bits, hand pressure, drill speed, and keeping the drill bits cool. With the right combination, you can successfully drill through stainless steel.
Center punch stainless steel before drilling holes. Mark the location of each hole you want to drill. Strike the center punch with a hammer in the center of each marked location. The punch will make a dent in the metal, which will stop your drill bit from wandering and scratching the surrounding metal.
Cutting oil is used to keep your drill bits cool. Heat is absorbed into drill bits when you drill holes in stainless steel, and the bits will quickly become dull or softened due to the extreme heat generated. Place two or three drops of cutting oil on the surface of the stainless steel before beginning to drill. Periodically add more drops of oil until you have drilled completely through the metal.
Titanium Step Bits
Titanium step bits are designed to drill through stainless steel. A step bit drills a small hole and gradually increases in size. Put on safety glasses and a long sleeve shirt before drilling. Hot metal shards can cut and burn your eyes or skin. Place a board behind the stainless steel when possible, and clamp it down. The board is used as a surface for the bit to grab into as it passes through the metal, and the clamps will stop the metal from spinning.
Use a good quality variable speed drill. Place the tip of the step bit into a dent you made with the center punch, and apply pressure to the drill. Begin drilling slowly and increase the drill speed. Your drill bit should be creating shards of metal while it is cutting. Drill at a medium speed until you have drilled through the metal. For large holes, use a carbide tip hole saw.
As stainless steel heats and cools, it becomes work hardened. Work hardening occurs when you drill too slow and the drill bit rubs the metal instead of cutting it, or when you drill too fast creating too much heat. Center punch the work hardened steel. Use a new carbide tip drill bit to drill a pilot hole. Continue increasing bit sizes, or use a step bit to gradually create a larger hole.
Use a drill press for multiple holes when possible. A drill press will give you more control, and eliminates hand fatigue.