Brief Description: Why I cant Step Drill where I want - Solution.
So, finally I know why I can't put a 5/8" Snap Bushing hole where I want it. In image 1 you can see the clamp is not symmetrically clamped. In this case the vibration of the step drill moves each side of the clamp towards each other. It needs to be clamped as in image 2. Even then I think things can move. I will be carfull on how I use these clamps.