Chapter 4 Measurement
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4.5.1 How to Use a Dial Indicator
The hand on the dial is actuated by a sliding
plunger. Place the plunger lightly against the work
until the hand moves. The dial face is turned until
the “0” line coincides with the hand. As the work
touching the plunger is slowly moved, the indicator
hand will measure movement.
The dial indicator can show the difference
between the high and low points, or the total run-
out of the piece in a lathe. When machining, adjust-
ments are made until there is little or no indicator
movement.
4.6 OTHER GAGING TOOLS
Industry makes wide use of other types of gag-
ing tools. Most of these tools are used for special
purposes and are not usually found in a school
shop. However, since you might need to use them in
industry, it is important to learn about such tools.
4.6.1 Air Gage
An air gage uses air pressure to measure hole
sizes and hard-to-reach shaft diameters, Figure 4-41.
This type of gage is especially helpful when mea-
suring deep internal bores. The basic operation of an
air gage is illustrated in Figure 4-42.
Figure 4-38. The two basic varieties of dial indicators.
A—Balanced indicators. B—Continuous indicators.
(L. S. Starrett Co.)
Figure 4-39. Mounting this dial indicator on a magnetic base
permits it to be attached to any ferrous metal surface. A push-
button releases the magnet.
Figure 4-40. This digital electronic indicator has numeric read-
outs and a conventional graduated dial.
(Federal Products Company)
A
B