A grinding wheel comprises an outer base with a first attached grain pad; and an inner frame with a second attached grain pad; and a spindle axis shared by the outer base and the inner frame, wherein at least one of the outer base and the inner frame can move independently along the shared spindle axis; and wherein the outer base, the inner frame, and the shared spindle axis all have a same center. A grinding system comprises an above said grinding wheel, and a wheel head attached to the shared spindle axis, capable of moving vertically, in addition to a motor driving the grinding wheel to spin; and a chuck table for fixing a wafer on top of the chuck table; wherein the grinding wheel overlaps a portion of the chuck table, each capable of spinning to the opposite direction of another.