Which tool is commonly used to measure crankshaft main journals?

Which tool is commonly used to measure crankshaft main journals?

• A. Vernier caliper
• B. Dial indicator
• C. Outside micrometer
• D. Feeler gauge

Answer: (C)

Measuring the diameter of crankshaft main journals requires a instrument that can precisely capture the external size at the bearing surface. The outside micrometer is the standard choice because it provides high-precision readings of external diameters, typically to 0.001 inch (or 0.01 mm). To get a reliable value, you measure at several points around the circumference to check for roundness and any ovality, since journals must be truly round to fit bearings smoothly. Vernier calipers can do the job in a pinch, but they’re not as precise for tight journal tolerances and readings can be less repeatable. A dial indicator is used for measuring deviations like runout or deformation, not the actual diameter. A feeler gauge checks gaps, not the exact external size of a journal.

Measuring the diameter of crankshaft main journals requires a instrument that can precisely capture the external size at the bearing surface. The outside micrometer is the standard choice because it provides high-precision readings of external diameters, typically to 0.001 inch (or 0.01 mm). To get a reliable value, you measure at several points around the circumference to check for roundness and any ovality, since journals must be truly round to fit bearings smoothly.

Vernier calipers can do the job in a pinch, but they’re not as precise for tight journal tolerances and readings can be less repeatable. A dial indicator is used for measuring deviations like runout or deformation, not the actual diameter. A feeler gauge checks gaps, not the exact external size of a journal.