GENERAL INFORMATION
1-18
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.
Although not as precise as a micrometer, they allow
reasonable precision, typically to within 0.05 mm
(0.001 in.). Most calipers have a range up to 150 mm
(6 in.).
Calipers are available in dial, venire or digital
versions. Dial calipers have a dial readout that
provides convenient reading. Venire calipers have
marked scales that must be compared to determine
the measurement. The digital caliper uses a
liquid-crystal display (LCD) to show the measurement.
Properly maintain the measuring surfaces of the
caliper. There must not be any dirt or burrs between
the tool and the object being measured. Never force
the caliper to close around an object. Close the caliper
around the highest point so it can be removed with a
slight drag. Some calipers require calibration. Always
refer to the manufacturer’s instructions when using a
new or unfamiliar caliper.
To read a vernire. Calipers refer to
Figure 21
. The fixed scale is marked in l-mm increments. Ten
individual lines on the fixed scale equal 1 cm. The movable scale is marked in 0.05 mm (hundredth)
increments. To obtain a reading, establish the first number by the location of the 0 line on the movable
scale in relation to the first line to the left on the fixed scale. In this example, the number is 10 mm. To
determine the next number, note which of the lines on the movable scale align with a mark on the fixed
scale. A number of lines will seem close, but only one will align exactly. In this case, 0.50 mm is the
reading to add to the first number. Adding 10 mm and 0.50 mm equals a measurement of 10.50 mm.