Which term describes a crankshaft journal that is not a perfect circle?

• A. Diameter
• B. Out-of-round
• C. Taper
• D. Surface finish

Answer: (B)

When a crankshaft journal isn’t a perfect circle, the shape is described as out-of-round (also called ovality). Journals are machined to be circular so the bearing clearance stays uniform around the entire circumference as the crank turns. If the circle is oval, the clearance varies as the journal rotates, leading to an inconsistent oil film, increased wear, and potential bearing damage. This condition is measured by checking how much the diameter changes around the circumference, not by a single diameter value. A taper would involve a gradual change in diameter along the length of the journal, not around its circumference, while surface finish refers to the roughness of the surface, not its circular shape.