What is cylindricity?

What is cylindricity?

• A. A form tolerance controlling the deviation of a cylindrical surface from a true cylinder along its axis.
• B. A positional tolerance for a cylindrical feature along its axis.
• C. A diameter tolerance for cylindrical features.
• D. A surface roughness specification for a cylinder.

Answer: (B)

Cylindricity is a form tolerance. It governs how much a cylindrical surface can deviate from a perfect cylinder along its length, not where the axis is located. The tolerance zone is a true cylinder coaxial with the feature’s reference axis, and every point on the surface must lie within that zone. This requirement blends straightness along the length and roundness around the axis into a single constraint, ensuring the surface stays true to a cylinder as you measure along its axis. It’s about the shape of the surface, not about locating or orienting the feature in space—that would be a positional tolerance.

Cylindricity is a form tolerance. It governs how much a cylindrical surface can deviate from a perfect cylinder along its length, not where the axis is located. The tolerance zone is a true cylinder coaxial with the feature’s reference axis, and every point on the surface must lie within that zone. This requirement blends straightness along the length and roundness around the axis into a single constraint, ensuring the surface stays true to a cylinder as you measure along its axis. It’s about the shape of the surface, not about locating or orienting the feature in space—that would be a positional tolerance.