A shaft coupling may be out of round if a dial indicator shows __________.

• A. No movement
• B. Any movement
• C. Large movement
• D. Cyclic movement

Answer: (B)

The main idea is runout: a shaft that isn’t perfectly circular or concentric will cause the dial indicator to show movement as the shaft rotates. If the surface were truly round, the indicator would read zero movement. Therefore, any movement on the dial indicates out-of-round conditions. No movement means the shaft is effectively round; large movement depends on how much deviation there is, and cyclic movement is a specific pattern of deviation but still falls under the presence of movement. The key takeaway is that any measurable movement reveals out-of-roundness.