How is a circularity tolerance defined?

• A. By specifying the minimum allowable diameter
• B. By defining how much a feature's outline can deviate from a perfect circle
• C. By setting limits on the overall size of the feature
• D. By determining the suitable surface finish for round parts

Answer: (B)

A circularity tolerance is defined by how much a feature's outline can deviate from a perfect circle. This tolerance ensures that the actual shape of the circular feature remains within a specified limit when compared to an ideal circle.

In practice, this means that if a circular feature, such as a hole or a shaft, is manufactured, the circularity tolerance allows for minor imperfections or deviations from a true circular shape, while still maintaining functional and aesthetic quality. The goal is to ensure that no point on the feature's outline is further than a defined radial distance from the center of the ideal circle.

By contrast, specifying a minimum allowable diameter relates more to dimensional tolerances rather than shape, and setting limits on overall size addresses general size requirements rather than geometric form. Determining surface finish focuses on the texture of the surface rather than its shape. Therefore, option B accurately captures the essence of circularity tolerance in geometric dimensioning and tolerancing.