Straightness (Flat Surfaces) — 

1. (ASME Y14.5M-1994, 6.4.1)

Straightness is the condition where an element of a surface or an axis is a straight line.

2. (ASME Y14.5M-1994, 6.4.2)

In this example, each line element of the surface must lie within a tolerance zone defined by two parallel lines separated by the specified tolerance value applied to each view. All points on the surface must lie within the limits of size and the applicable straightness limit.

The straightness tolerance is applied in the view where the elements to be controlled are represented by a straight line.

Straightness (Surfaces Elements) — 

In this example, each longitudinal element of the surface must lie within a tolerance zone defined by two parallel lines separated by the specified tolerance value. The feature must be within the limits of size and the boundary of perfect form at MMC. Any barreling or waisting of the feature must not exceed the size limits of the feature.

Straightness (RFS) — 

Outer Boundary = Actual Feature Size + Straightness Tolerance

In this example, the derived median line of the feature’s actual local size must lie within a tolerance zone defined by a cylinder whose diameter is equal to the specified tolerance value regardless of the feature size. Each circular element of the feature must be within the specified limits of size. However, the boundary of perfect form at MMC can be violated up to the maximum outer boundary or virtual condition diameter.

Straightness (MMC) —