General Information
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.
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