Which type of alignment setup would most commonly apply a bar sag measurement?

In the context of alignment setups, bar sag measurement is most commonly associated with cross dial alignment. This method utilizes a dial indicator mounted on a cross bar, which allows for accurate measurement of misalignment between two shafts or components. When using cross dial alignment, the bar's sag is a critical factor because it can influence the readings obtained. Ensuring that the bar is as level as possible minimizes errors and enhances the precision of the alignment process. This technique is particularly effective in situations where direct line-of-sight measurements between the components are not feasible, and the sag provides a means to account for any deflections or misalignments.

Other methods, such as vertical alignment, horizontal alignment, and face alignment, do not specifically utilize a sag measurement to the same extent. Vertical and horizontal alignments primarily focus on the vertical or horizontal positioning of objects rather than incorporating the concept of bar sag. Face alignment is more concerned with the face-to-face contact of two surfaces, also not traditionally incorporating sag, making cross dial alignment the most applicable choice for this measurement approach.