For lateral runout, a technician should use a

• A. Dial Indicator
• B. Micrometer
• C. Torque wrench
• D. Ruler

Answer: (A)

Measuring lateral runout requires detecting small side-to-side movement of a rotating surface as it turns, so you need a tool that translates tiny displacements into a readable value. A dial indicator fits this purpose because its sensitive plunger contacts the surface and, as the part rotates, the dial shows minute deflections. By mounting the indicator and rotating the wheel, you can see the peak-to-peak movement and quantify the runout accurately. A micrometer measures a fixed dimension at one point and isn’t designed to track movement during rotation; a torque wrench measures torque, not surface deviation; and a ruler is far too coarse to resolve the small, dynamic variations involved in runout.