TS ISO 5459

TS ISO 5459 is a standard on datums and datum systems used in geometrical tolerancing, i.e. the reference framework that lets a technical drawing define a feature’s position, orientation, and relationship to other features. In general technical drawing practice, datums are central because geometric tolerances are not only about size; they are also about how a part is located and controlled in assembly and function.

How datums and datum systems work

In general engineering terms, a datum is a chosen reference feature such as a surface, axis, or point from which other features are related. A datum system goes further by combining multiple references to establish a coordinated frame of reference, typically resolving degrees of freedom step by step. That distinction matters whenever a part must fit another component, be aligned in manufacture, or be inspected consistently.

According to the supplied scope, this standard covers the references that need to be designated in technical drawings in the general machine-manufacturing field, together with definitions and the structural arrangement of datum systems. It therefore supports a common way to identify and present the references used for geometrical tolerances, rather than treating them as informal drawing notes.

• Helps technical drawings express the reference basis behind geometrical tolerances.
• Clarifies the distinction between a single datum feature and a complete datum system.
• Supports consistent interpretation in machine manufacturing and inspection.
• Used alongside related drawing and tolerancing standards such as ISO 128, ISO 129 and ISO 1101.