ISO 21204:2020

This document defines a number of specification operators for the specification of extended edge transition features between features. An edge transition feature is an integral feature connecting two adjacent integral features. The extended edge transition feature includes portions of the adjacent features. All these specifications apply to any line in a defined direction in the extended edge transition feature. This document also defines the specification modifiers and the drawing indications for such transition specifications. The proportions and dimensions of the graphical symbols to be used are also specified. The specifications defined in this document are suitable for relatively simple edge transition functions, for example ensuring assembly without interference. For more complex functions, geometrical tolerancing offers more precise tools. This document is by intention limited to only edge transition features between two planes and between a cylinder and a plane nominally perpendicular to it. Annex A gives the first approach for an algorithm to identify toleranced features and adjacent reference sections. This algorithm is subject to change as more experience is gathered. This document provides a set of tools to express several transition specifications. It does not present any information on the relationship between a function or a use and a transition specification. NOTE 1 Corners (the transition between three or more features) are not edge transition features and are consequently not covered by this document. NOTE 2 An edge transition feature exists between two single features. A defined edge transition feature has a defined nominal shape and is not sharp (r = 0).