In cross-dial reverse reading for vertical alignment, where should dials be set?

In cross-dial reverse reading for vertical alignment, setting the dials at the 12 o'clock position with a predetermined sag is essential for achieving accurate measurements. This positioning allows for consistency in reading the dials, as it provides a standardized reference point from which the alignment can be evaluated.

By using the 12 o'clock position, any variances in vertical alignment can be more readily observed and measured. The predetermined sag compensates for any expected deflection due to gravitational effects or the weight of connected components, enabling a more accurate assessment of how the machinery settles under its operational load. This approach ensures that readings can be duplicated and compared effectively, enhancing the reliability of the alignment process.

In contrast, other options may not provide the same level of precision. Random positions could introduce variability and lead to inconsistent measurements. The 6 o'clock and 9 o'clock positions, without the context of sag, may not fully account for the dynamics at play and could miss critical adjustments needed for optimal alignment. Therefore, using the 12 o'clock position with predetermined sag enhances the effectiveness and accuracy of the alignment procedure.