Bar sag is ________ to the reading on dial B.

In the context of dial indicators used in millwright practices, bar sag refers to the deflection or droop that occurs in a support or structural member when a load is applied. Specifically, when measuring the alignment or positioning of shafts and other components, the readings taken on a dial indicator can be affected by this sag.

When determining the correct reading to account for bar sag, this deflection must be accounted for in the final measurements. This means that the observed reading on dial B, which is measuring the height or alignment, will need to be adjusted downward to accommodate for the sagging of the bar. Therefore, the sag is taken away from the reading on dial B to ensure accurate alignment measurements. This ensures that any misalignment attributed to the sag is properly corrected, leading to more precise and effective maintenance or installation procedures.