The manufacture of magnetic disks for disk drives requires formation or servo tracks in a concentric pattern on the disk. Certain types of beam apparatuses for forming feature patterns on a disk shaped substrate, such as might be used in hard disk manufacture, however, provide spiral patterns. A ramp type deflection signal therefore is used to deflect the beam so as to form one circular pattern during each rotational cycle, and thereby convert the spiral pattern to a pattern comprising a series of circles.