What type of misalignment do dial indicator readings taken on the face of the coupling indicate when rotated through 180 degrees?

Dial indicator readings taken on the face of a coupling when rotated through 180 degrees primarily indicate angular misalignment. When measuring a coupling, if the readings change significantly as the dial indicator is rotated, this reflects the angular relationship between the shafts and the coupling faces.

Angular misalignment occurs when the shafts are not aligned in the same plane, causing a change in the reading around the coupling's circumference. As the indicator is rotated through 180 degrees, if there is a consistent variation in the measurements, it confirms the existence of this type of misalignment.

Understanding this principle is important in millwright work, as angular misalignment can lead to increased wear and tear on bearings and other components, ultimately impacting the efficiency and longevity of machinery.