How to Measure and Correct Tool Runout
What Tool Runout Does to Your Holes Tool runout is the amount the drill wobbles off its true center of rotation. A drill that runs true produces a round hole at the nominal diameter. A drill with runout produces an oversized, bell-mouthed, or irregular hole. I have measured the relationship between runout and hole size many times. A runout of 0.02mm at the drill tip produces a hole that is 0.03-0.05mm oversized. The extra material removal wears the tool faster and leaves a poorer surface finish. ...