Special Cased Instruments, Continued
Center disks prevent the enlargement of a hole when concentric circles and
arcs are drawn. They are usually very small with a transparent center and
three needlepoint legs for holding a position on the drawing surface. Position
the center disk carefully on the drawing surface, place the compass needle
inside the center of the disk, and rotate the compass to draw concentric
Figure 2-37 shows an enlargement of a center disk.
Figure 2-37. A center disk.