LO 5-4 Define concentricity and explain methods to measure it

LO 5-04: Define concentricity and explain methods to measure it

Dial Bore Gauges

Dial bore gauges are used for precision measurement of inside diameters of cylinder bores. These gauges use a dial indicator attached to a long handle to quickly inspect a cylinder, either new or worn, for cylinder concentricity, wear resulting in taper, or barrel-shaped cylinder dimensions. When the dial indicator is calibrated with a standard dimension ring gauge having the same specific diameter of a cylinder, the gauge can quickly determine whether the cylinder is bored to specifications. An alternative method is to zero the bore gauge to a dimension measured by a micrometer. Plunger extensions of various lengths can be interchanged on a single dial bore gauge to inspect cylinders of a wide range of diameters.

When placed inside a cylinder bore, the smallest reading on the dial gauge is observed at the narrowest point in the cylinder when the gauge is square, or at 90 degrees perpendicular to the cylinder bore. This position is found by rocking the dial bore gauge lever back and forth inside the cylinder FIGURE 29. The dial indicator pointer will move to its smallest number and then change direction on either side of 90 degrees, perpendicular to the cylinder where the measurement is taken. To understand how a dial bore gauge is used to measure cylinder dimensions, follow the outline describing its use in SKILL DRILL 5-2.

FIGURE 05-29: The narrowest dimension of a cylinder bore will be at 90 degrees or perpendicular to the axis of the cylinder bore.

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