How is straightness tolerance inspected?

How is straightness tolerance inspected?

• A. By checking curvature across the surface.
• B. By checking the deviation of a straight feature (line or axis) from a true straight line along its length.
• C. By measuring parallelism to a datum.
• D. By measuring perpendicularity to a datum.

Answer: (B)

Straightness tolerance controls how much a line element of a feature (its axis or a defined straight line on the surface) can deviate from an ideal straight line as you move along its length. To inspect it, you establish a true straight line that follows the intended path of the feature and then measure how far points on the actual feature stray from that line along its length. The largest deviation, measured perpendicularly to the true line, must fall within the specified tolerance. In practice you might use a CMM, a straight edge with a dial indicator, or a scanning probe to trace along the feature and compare against the ideal line. This focuses on the one-dimensional straightness of the feature, unlike curvature, parallelism, or perpendicularity, which involve different geometric relationships.

Straightness tolerance controls how much a line element of a feature (its axis or a defined straight line on the surface) can deviate from an ideal straight line as you move along its length. To inspect it, you establish a true straight line that follows the intended path of the feature and then measure how far points on the actual feature stray from that line along its length. The largest deviation, measured perpendicularly to the true line, must fall within the specified tolerance. In practice you might use a CMM, a straight edge with a dial indicator, or a scanning probe to trace along the feature and compare against the ideal line. This focuses on the one-dimensional straightness of the feature, unlike curvature, parallelism, or perpendicularity, which involve different geometric relationships.