Figure 3-23. Scribing a Circle with Dividers
(3) Sharpen divider points with a small oil
stone, Federal Specification SS-S-736, moistened with
engine oil, MIL-L-6082. Keep points toward inside of
legs so that points meet when legs are closed. Hold
dividers stationary and stroke with oil stone.
3-8. Calipers. Calipers are used to measure
diameters. Outside calipers measure outside diameters.
Inside calipers measure inside diameters. Simple
calipers are used along with a scale to find the
measurement. Slide calipers and vernier calipers have
their own scales. They are more accurate than a ruler,
and when used properly with a micrometer, they can be
used to take measurements to within 0.0001 inch.
a. Types of Calipers. There are a variety of caliper
styles available to the aircraft repairer. The following
paragraphs describe these types.
(1) Simple calipers. The simple outside
calipers are bowlegged. Those used for inside
diameters have straight legs with feet turned outward.
Calipers are adjusted by pulling or pushing the legs to
open or close them. This type is shown in figure 3-24.
(2) Spring-joint calipers. The spring-joint
calipers have the same type of legs, but are joined by a
strong spring hinge, screw, and adjustment nut. They
are shown in figure 3-25.
Figure 3-24. Simple Calipers
Figure 3-25. Spring-Joint Calipers