An apparatus for applying a lightly scratched surface to a metal sample comprises a motor, a disk, a frame, a motion guidance unit, and a plurality of springs. The motor may provide a rotational motion to the disk which includes abrasive elements configured to create a plurality of microscopic scratches on the surface of the metal sample. The frame may include a bottom wall with an opening in which the motor is positioned. The motion guidance unit may retain the frame and guide the motion of the motor across the surface of the metal sample. The plurality of springs may couple the motor to the bottom wall of the frame in order to suspend the motor within the opening of the bottom wall and to allow lateral motion of the motor and the disk while the motor is rotating.