Which type of bearing uses cylinders to maintain the separation between moving parts?

• A. Flat key
• B. Square key
• C. Roller bearings
• D. Ball bearings

Answer: (C)

Rolling bearings keep moving parts from rubbing directly by using rolling elements between the parts. When those rolling elements are cylindrical, the bearing is a roller bearing. The rollers run between inner and outer races, carrying the radial load and maintaining separation while the shaft rotates, which gives good load capacity and stiffness. The other items aren’t bearings: flat or square keys are fasteners that lock components to a shaft rather than provide rolling contact, and ball bearings use balls, not cylinders. So the type that uses cylinders to maintain the separation is roller bearings.