There is disclosed herein a method and apparatus for centering a disk on a spindle, a spinstand and a method of testing with a spinstand. The method of centering includes attaching the disk to the spindle with a stick-slip clamp. A vector is determined by which the centre of the disk is displaced from the spindle axis and the vector is aligned with a movably mounted piezo actuator. A voltage is then applied to the piezo actuator to cause the piezo actuator to apply an impulse to the edge of the disk to cause the disk to slip in the clamp and reduce the displacement of the disk.