  ## Shape and position tolerances questions and answers

November 13, 2023

31. What is the definition of symmetry tolerance zone?

A: the tolerance zone is the area between two parallel planes (or straight lines) whose distance is the tolerance value t and which are symmetrically arranged relative to the datum center plane (or center line or axis). If two directions that are perpendicular to each other are given, then It is the area within the square prism whose normal cross section is the tolerance value t1×t2.

32. In positional degree, what is the definition of the positional degree tolerance zone of a point?

A: the tolerance zone is the area within a circle or sphere with a diameter of the tolerance value t and centered on the ideal position of the point.

33. In positional degrees, what is the definition of the tolerance zone of a line's positional degree 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 symmetrically arranged with the ideal position of the line as the center; when two mutually perpendicular planes are given direction, it is the area within the square prism whose normal cross-section is the tolerance value t1×t2 and with the ideal position of the line as the axis.

34. In positional degree, what is the definition of the tolerance zone of the positional degree of a line in any direction?

A: the definition of the tolerance zone for the position of the line in any direction - the tolerance zone is the area within the cylindrical surface with a diameter of the tolerance value t and with the ideal position of the line as the axis.

35. In circular runout, what is the definition of the tolerance zone for radial circular runout?

A: the tolerance zone is the area between two concentric circles in any measurement plane perpendicular to the datum axis, the radius difference is the tolerance value t, and the center of the circle is on the datum axis.

36. In circular runout, what is the definition of the tolerance zone for end face circular runout?

A: the tolerance zone is a cylindrical surface area with a width t along the generatrix direction on the measuring cylindrical surface at any diameter position coaxial with the reference axis.

37. In total runout, what is the definition of the tolerance zone for radial total runout?

A: the tolerance zone is the area between two cylindrical surfaces whose radius difference is the tolerance value t and is coaxial with the datum axis.

38. In total runout, what is the definition of the tolerance zone for full end face runout?

A: the tolerance zone is the area between two parallel planes that are distanced by the tolerance value t and perpendicular to the datum axis.

39．What is the theoretical correct size?

A: for the position, contour or inclination of an element, its size is determined by the theoretical correct position contour or angle without tolerance. This size is called the theoretical correct size.

Theoretically correct dimensions should be bounded by a frame. The actual size of the part is limited only by the position, profile or inclination tolerance in the tolerance frame.

40. What must you know when adopting the maximum entity requirement?

A: the given shape or position tolerance value is given under the premise that the measured element is in the maximum solid state, or the datum element is in the maximum solid state, so its symbol is immediately after the tolerance value.

The maximum solid actual state of the measured element is controlled by the maximum solid actual boundary formed by the maximum solid size and the geometric tolerance value. When the measured element is in this effective state, the assembly gap is minimum. When the actual size of the measured feature deviates from its maximum physical size, the shape or position tolerance value can exceed the allowed value, but it must be within the effective boundary. under normal circumstances, when the measured element is in the minimum solid state, the compensation amount obtained from the geometric tolerance is the largest.

When a datum feature adopts the maximum physical requirement, it is determined by the requirements of the datum feature itself. If the containment requirement is adopted, the datum element is controlled by its maximum physical boundary. When the actual size deviates from the maximum physical size, the measured element can be compensated. If the inclusion requirement is not adopted, in addition to the maximum physical size of the datum feature, the boundary should also consider the influence of unindicated geometric tolerances. When the datum element is controlled by the maximum physical effective boundary formed by the combination of its maximum physical size and the unindicated geometric tolerance value, when the actual size deviates from the maximum physical effective size, the measured element can obtain a compensation value.