What is runout?

What is runout?

• A. A tolerance for a feature’s deviation as the part rotates about a datum axis; there are types: circular runout and total runout.
• B. A tolerance for the flatness variation on a face.
• C. A tolerance for the perpendicularity of datum features.
• D. A size tolerance for hole diameter.

Answer: (C)

Runout is a GD&T control that limits how far a feature’s surface deviates while the part is rotated about a datum axis. It captures how much the feature wobbles or runs out from a true circle as you spin the part, essentially tying the measurement to rotation about a reference axis. There are two forms: circular runout, which looks at a single feature around its axis during rotation, and total runout, which extends the tolerance to the entire surface as it rotates. The key idea is that runout governs the coaxial behavior of a feature with respect to the datum axis, not just a single dimension or a flatness or orientation requirement. This concept is different from flatness, which only concerns how flat a face is; perpendicularity, which controls the angle between features and a datum, and size tolerances, which specify allowable limits for a dimension like a hole’s diameter. Runout specifically addresses the behavior of a feature as the part rotates, enforcing consistent coaxiality and circularity relative to the reference axis.

Runout is a GD&T control that limits how far a feature’s surface deviates while the part is rotated about a datum axis. It captures how much the feature wobbles or runs out from a true circle as you spin the part, essentially tying the measurement to rotation about a reference axis. There are two forms: circular runout, which looks at a single feature around its axis during rotation, and total runout, which extends the tolerance to the entire surface as it rotates. The key idea is that runout governs the coaxial behavior of a feature with respect to the datum axis, not just a single dimension or a flatness or orientation requirement.

This concept is different from flatness, which only concerns how flat a face is; perpendicularity, which controls the angle between features and a datum, and size tolerances, which specify allowable limits for a dimension like a hole’s diameter. Runout specifically addresses the behavior of a feature as the part rotates, enforcing consistent coaxiality and circularity relative to the reference axis.