The most common of the mechanical distance measurement methods is the benchmark gages. Figure 3.42 shows some standard tooling balls. These tooling balls are 1/2-inch-diameter stainless steel and are permanently fixtured to the foundation and the machine housing near the bearings. Figure 3.43 shows two standard configurations for installation of the tooling balls, or benchmarks.

Figure 3.42: Standard diameter tooling balls used as benchmark gauges.

Figure 3.43: Installation of tooling balls or benchmarks ( a) standard configuration for accessible bearing housing; ( b) dual arrangement when bearing housings are not accessible.

When the cold alignment is complete, the reference dimensions A and B are measured with a linear gage that mates to the spheres of the tooling balls. Linear distances can be accurately measured to .001 inch or less. The angles ? and ? are also measured with an inclinometer.

When the machine is operating in the hot condition, the dimensions A and B are again measured resulting in differences ?A and ?B. The angles ? and ? do not need to be remeasured because their changes are very small and insignificant. A graphical construction can now be done to determine the vertical and horizontal movement of the housing relative to the foundation, Fig. 3.44.

Figure 3.44: Graphical calculation of housing movement using benchmark gauges.

On grid paper, the vectors A and B are laid out at angles ? and ? relative to the foundation. The length...