Dial bar sag is applied to which readings when doing cross dial readings?

Dial bar sag refers to the deflection or bending of the dial bar due to the weight or applied load. In the context of cross dial readings, especially when measuring alignments and settings, accurate readings are crucial for the reliability of the measurement.

The correct answer indicates that both the A and B dials need to be referenced at both the 6 and 12 o'clock positions. This practice ensures that any sag affecting the readings at either position is accounted for. By taking measurements at both the 6 o'clock and 12 o'clock positions, you can apply corrections based on how the sag may influence the readings. This dual measurement approach compensates for any potential inconsistencies introduced by the sag across different angles.

Using both dials allows for a comprehensive assessment of the component's alignment while ensuring that variations caused by dial bar sag are minimized and properly evaluated. This method is especially important in precision work, where even slight errors can lead to larger issues in mechanical systems.