Cased Instruments, Continued
Extension bars extend the range of a compass so you can draw larger circles.
Care for an extension bar as you would any other cased instrument.
Figure 2-27 shows a compass with and without an extension bar.
Figure 2-27. A. A standard
length compass. B. A
standard compass with an
Draw an extremely large circle and arcs with a beam compass. The length of
the beam that attaches the nibs and needle is the only limitation in the size of
the radius of an arc or diameter of a circle. There are several styles and
levels of sophistication. Care for a beam compass as you would any other
Figure 2-28 shows two types of beam compasses.
Figure 2-28. Beam