(b) To avoid kinking tapes, pull them straight out from their cases-do
not bend them backward. With the windup type, always turn the crank clockwise-
turning it backward will kink or break the tape. With the spring-wind type, guide
the tape by hand. If it is allowed to snap back, it may be kinked, twisted, or
otherwise damaged.
comparing dimensions or sizes with standards such as a graduated rule.
(1) Outside calipers. Outside calipers (fig 50) are used to measure
distances over and around adjacent surfaces and to transfer the measurements to a
rule. Several types are made in different sizes to accommodate a wide range in
measurements. The size of the caliper is expressed in terms of the maximum
dimension it is capable of measuring. A 3-inch caliper, for example, will measure
a distance of 3 inches. Actually, the maximum capacity of a caliper will be
greater, often as much as one-third. This means that a 3-inch caliper will
actually measure up to 4 inches; however, it is not recommended that you use a 3-
inch caliper to measure 4 inches, since you may spring the legs resulting in an
inaccurate measurement.
Figure 50.
Calipers-noncalibrated.
(2) Inside calipers. Inside calipers (fig 50) have the same general
function as outside calipers, except, that where the latter are used in measuring
distances over outside surfaces, the inside caliper is used in measuring distances
between inside surfaces. The points are rounded so that they are slightly ball-
shaped. This ball shape establishes the point of contact, and in inside
callipering where the surfaces are likely to have an inside curvature an error may
occur if the radius of the hole being callipered is less than the radius of the
points. Some inside calibers are equipped with an adjusting screw on one leg which
provides a fine adjustment of the caliper legs.
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