November 10, 2023

**21. What is the definition of flatness tolerance zone?**

A: the tolerance zone is the area between two parallel planes whose distance is the tolerance value t.

**22. What is the definition of roundness tolerance zone?**

A: the tolerance zone is the area between two concentric circles on the same normal section whose radius difference is the tolerance value t.

**23. What is the definition of cylindricity tolerance zone?**

A: the tolerance zone is the area between two coaxial cylindrical surfaces with a radius difference t.

**24. What is the definition of line profile tolerance zone?**

A: the tolerance zone is the area between two envelopes enclosing a series of circles with a diameter of tolerance value t. The centers of the circles should be located on the ideal contour line relative to the datum. When there are position requirements for the ideal contour line relative to the datum, the ideal contour line refers to the relative datum ideal contours for ideal locations.

**25. How is line profile applied?**

A: in any section parallel to the orthographic plane, the actual contour line must lie between two envelopes enclosing a series of circles with a diameter of a tolerance value of 0.04 and whose center is on the ideal contour line.

**26. What is the definition of surface profile tolerance zone?**

A: the tolerance zone is the area between two envelope surfaces that envelop a series of balls with a diameter of tolerance value t. The centers of the balls should be located on the ideal contour surface.

Note: When the measured contour surface has position requirements relative to the datum, the ideal contour surface refers to the theoretical contour surface in an ideal position relative to the datum.

**27. In parallelism, what is the definition of the tolerance zone in a given direction?**

A: when a direction is given, the tolerance zone is the area between two parallel planes whose distance is the tolerance value t and parallel to the datum plane (or straight line or axis). When two directions that are perpendicular to each other are given, It is the area within the square prism whose normal cross-section size is the tolerance value t1×t2 and is parallel to the datum axis.

**28. In parallelism, what is the definition of the tolerance zone in any direction?**

A: the tolerance zone is the area within the cylindrical surface whose diameter is the tolerance value t and is parallel to the datum axis.

**29. In verticality, what is the definition of the tolerance zone in a given direction?**

A: when a direction is given, the tolerance zone is the area between two parallel planes (or straight lines) that are distanced by the tolerance value t and are perpendicular to the datum plane (or straight line, axis); when two mutually perpendicular When the direction is , it is the area within the square prism whose normal cross-section is the tolerance value t1×t2 and is perpendicular to the datum plane.

**30. In verticality, what is the definition of the tolerance zone in any direction?**

A: the tolerance zone is the area within the cylindrical surface whose diameter is the tolerance value t and is perpendicular to the datum plane.