9.1 Definitions

Actual local size (two-point size) Any individual distance at any cross-section of a feature of size (see p. xviii), i.e. any size measured between any two opposite points (twopoint measurement) (ISO 286, ISO 2692) (Fig. 9.1).

Figure 9.1: Sizes and conditions of a feature with a related geometrical tolerance

Each feature of size (see p. xviii) of an individual workpiece theoretically has an infinite number of actual local sizes.

In the past, the definition of actual local size was not unambiguously standardized. The problems were the definitions of "opposite" and of the directions of the cross-sections (see 8.3.1). The new standard ISO 14 660-2 gives definitions of two-point size and various other sizes. The two-point size is the default (i.e. if not otherwise specified).

Maximum material condition (MMC) The state of the considered feature of size in which the feature is everywhere at that limit of size where the material of the feature is at its maximum, e.g. minimum hole diameter and maximum shaft diameter (ISO 2692). The actual axis of the feature need not be straight.

Mating size for an external feature The dimension of the smallest perfect feature (e.g. cylinder or two parallel opposite planes) that can be circumscribed about the feature so that it just contacts the surface at the highest points (Fig. 9.1).

Mating size for an internal feature The dimension of the largest perfect feature (e.g. cylinder or two parallel opposite planes) that can be inscribed within the feature...