Principles and Fundamental Rules

This reference describes the basic principles and fundamentals for geometrical tolerancing.

All the dimensions, forms, orientations and position specifications (either on a geometric feature or on a geometric feature group of a part) are independent (see ISO 8015).

The dimensions of the features and their geometry are independent, regarding the form, the orientation and the position (see ISO 8015).

Each dimension shall have a tolerance, except for the dimensions specially identified as reference, maximum, minimum, or stock (commercial stack size). The tolerance may be applied directly to the dimension (or indirectly in case of basic dimensions), indicated by a general note, or located in a supplementary block of the drawing format, see ANSI Y14.1, ASME Y14.5M-1994).

Dimensioning and tolerancing shall be complete so there is full understanding of the characteristics of each feature. Neither scaling (measuring the size of a feature directly from an engineering drawing) nor assumption of a distance or size is permitted, except as follows: non-dimensioned drawings, such as loft, printed wiring, templates, and main layouts prepared by an stable material, are excluded provided the necessary control dimensions are specified, (ASME Y14.5M-1994).