I like using the step (taper) bits for drilling rivets. Once the rivet is ready (punching out the mandrel or center punching, the step bit chews through the metal well without chattering like a twist bit. When you get very close, the angle up to the next diameter hole does a great job of cutting the "washer" off without much damage to the parent material. By having the step in the bit, it acts as a centering guide as you drill through increasing diameters until you reach the desired size. I have had issues with twist bits sliding off center if the parent material is softer than the metal being drilled and it doesn't jar you like a twist bit can when the bit almost pops through the metal and grabs. Bonus, I only make one trip to the bench to get the "right" size bit, unlike twists bits where I seemingly always have the wrong size.