USE/CARE OF HANDTOOLS & MEASURING TOOLS - OD1621 - LESSON 3/TASK 1
(a) Spring Caliper.
1 The spring caliper is available in sizes from 2 to 8
inches.
The friction of the adjusting nut and screw works against the
tension of the spring which holds the legs in any set position. This type
of inside caliper is known as the toolmaker's spring caliper.
2 Thread spring calipers are used to measure diameter and
distances in tapped holes.
The ends of the legs of thread calipers are
shaped to a fine point so that exact contact may be made between threads.
(b) Firm Joint Caliper.
The firm joint type is available in a
number of sizes from 3 to 24 inches. This type of caliper is equipped with
a nut and stud that provides sufficient friction to hold the legs in any set
position.
Some variants of this type of caliper are equipped with an
adjusting screw for fine adjustments.
(c) Transfer Firm Joint Caliper.
Inside transfer firm joint
calipers are shaped for inside measurements and are used for measuring
recesses where the setting cannot be transferred to a scale directly because
the legs must be collapsed to remove them from the work.
Hermaphrodite calipers (figure 176 on
the previous page) are a cross between a divider and an inside caliper,
having one leg of each. These calipers are used for scribing parallel lines
from an edge, or for locating the center of cylindrical work.
Some are
equipped with an adjustable point.
(5) Trammels. A trammel is a tool used for the same purposes as a
divider or caliper, but usually for distances beyond the range of either of
these instruments.
A steel beam trammel with all of the attachments
required in measuring and layout work is shown in figure 177 on the
following page. The instrument consists of a rod or beam to which trams may
be clamped. These steel beams will range in length from 9 to 20 inches, but
may be increased further through the use of extensions.
Longer beams are
often made of wood. The trams carry spring chucks in which divider points,
caliper points, and ball points may be inserted so that the trammel may be
readily converted from a divider to
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