General
1-20
PRECISION MEASURING
TOOLS
The ability to accurately measure
components is essential to perform
many of the procedures described in this
manual. Equipment is manufactured to
close tolerances, and obtaining
consistently accurate measurements is
essential to determine which
components require replacement or
further service. Each type of measuring
instrument is designed to measure a
dimension with a certain degree of
accuracy and within a certain range.
When selecting the measuring tool,
make sure it is applicable to the task. As
with all tools, measuring tools provide
the best results if cared for properly.
Improper use can damage the tool and
cause inaccurate results. If any
measurement is questionable, verify the
Measurement, using another tool. A
standard gauge is usually provided with
micrometers to check accuracy and
calibrate the tool if necessary. Precision
measurements can vary according to the
experience of the person performing the
procedure. Accurate results are only
possible if the mechanic possesses a
feel for using the tool. Heavy-handed
use of measuring tools produces less
accurate results. Hold the tool gently by
the fingertips to easily feel the point at
which the tool contacts the object. This
feel for the equipment produces more
accurate measurements and reduces
the risk of damaging the tool or
component. Refer to the following
sections for specific measuring tools.
Feeler Gauge
Use feeler or thickness gauges (Figure19) for
measuring the distance between two
surfaces.
A feeler gauge set consists of an assortment
of steel strips of graduated thickness. Each
blade is marked with its thickness. Blades can
be of various lengths and angles for different
procedures. A common use for a feeler gauge
is to measure valve clearance. Use wire
(round) type gauges to measure spark plug
gap.
Calipers
Calipers (Figure 20) are excellent tools for
obtaining inside, outside and depth
measurements.
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