LO 5-3 Identify and describe common instruments and techniques to make linear precision measurements

LO 5-03: Identify and describe common instruments and techniques to make linear precision measurements

Gauges Versus Measuring Tools

Before examining the construction, operation, and applications for the above-listed tools, it is helpful to distinguish between a gauge and a measuring tool. Measuring tools determine actual dimensional sizes, physical quantities, and distances or volume, and the results are reported numerically FIGURE 3. For example, the thickness of textbook paper is 0.1 mm or 0.0039". Gauges, however, compare a dimension to a designated standard. For example, when determining whether a cap screw for a cylinder head is deformed by stretching, the length of the cap screw could be measured with an accurate ruler. The measured length is then compared with specifications to check its serviceability. Alternatively, a gauge comparing acceptable limits for the cylinder cap screw length is also used. The gauge would not produce a measurable quantity for length, but in this case, a gauge can more quickly determine whether the bolt is deformed and stretched beyond acceptable limits FIGURE 4.

FIGURE 05-4: An example of a gauge to measure head bolt length. This go-no-go gauge is used to determine whether a cap screw is excessively distorted or reusable.

FIGURE 05-3: This tool measures valve spring length and spring tension. Results are reported numerically on a dial (pressure or weight at specific spring length) or on a graduated scale with markings indicating length.

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