Which type of geometric tolerance controls the variation of straightness and circularity relative to a cylindrical part's centerline?

Runout tolerance is specifically designed to control the variation in both straightness and circularity with respect to a cylindrical part's centerline. It assesses how much the part deviates from the desired form during rotation around its centerline. This type of tolerance ensures that the cylindrical surface remains consistently true to its intended path, which is essential for parts that are expected to rotate, such as shafts or bearings.

In more detail, runout tolerance encompasses two critical aspects: circular runout and total runout. Circular runout measures how much a part varies when it is rotated about its axis, ensuring that every cross-section remains within a specified tolerance. Total runout incorporates both variations in circularity and straightness over the entire length of the feature, helping ensure the part's overall functionality and performance.

Understanding runout tolerance is crucial for ensuring that components will fit properly and function as intended within assembled systems, particularly where rotational dynamics are involved.