I tend to get these weird scratches on the aluminum when countersinking. It obviously can't be the bit, and the location puts the scratches somewhere between the bit and the cage. The only thing I can figure what is causing it is probably the chips coming out of the hole somehow get swept around the countersink between the bit and cage. I would expect to see concentric circles, which are there, but the irregularly shaped scratch is the real mystery. Is my technique messed up somehow? Does anyone have any insight into how or why this is happening?