What does "total runout" measure?

• A. The total size difference between two features
• B. The variation of a feature during a static inspection
• C. The total variation of a feature as it rotates
• D. The overall symmetry of a feature

Answer: (C)

Total runout measures the total variation of a feature as it rotates. This geometric tolerance specifically assesses how much the surface of a feature deviates from its desired path when that feature, such as a shaft or a circular part, is rotated about a given axis.

Total runout accounts for both circular runout (variation at different radial positions along the surface) and axial movement (deviation in the vertical direction) during the full rotation of the part. This is crucial in ensuring that rotating components meet performance standards, especially in applications where precision and smooth operation are required, such as in bearings or wheels.

This tolerance is significant because it captures the combined variations that arise not only from circular form but also from the alignment to the axis, thereby ensuring that the part functions correctly during use. Proper use of total runout helps in optimizing both the manufacturing process and the quality of the final product.