Dial bar sag can occur with which of the following conditions?

Dial bar sag can occur under various conditions, including all options presented. Large diameters and long spans can introduce significant weight and leverage, causing the dial bar to bend or sag as a result of gravity acting on the length of the bar. In smaller diameters and short spans, while less likely, there could still be some degree of sag due to the load it supports, especially if the bar is not adequately supported at all points or if it is made from a material that does not have high rigidity. Additionally, measurements taken at the 12 and 6 o'clock positions can contribute to perceived sag, as they may reveal inconsistencies in alignment or leveling that indicate bar sag.

Ultimately, understanding that sag can manifest in various situations allows for a more comprehensive approach to measurements in millwright work. By recognizing this, millwrights can take corrective actions to ensure better accuracy in their setups, regardless of the specific conditions present.