You can adjust the angle or position of the front and rear of the clamp. I have both R and L helical clamps for mine, plus I use different diameter shafts, so everyone involves resetting the clamp holder angle. I do have pencil marks for the common settings, but initially, put in what ever shaft you are using, put a feather in the clamp and loosen the two "dials" at the ends of the clamp holder, then adjust them while watching how the quill of the feather contacts the shaft, it should end up with the quill on the centerline of the shaft at both ends AND the quill making good contact its full length. You have to make the adjustments with a feather in the clamp as the thickness of the quill alone makes a big difference.