TS ISO 5458

TS ISO 5458 is a technical drawing standard focused on geometrical tolerancing for positional tolerances, setting out the principles used to assess where geometric features are located relative to one another. In practical drafting terms, it helps define not only the size of features such as holes, shafts, axes, or centre planes, but also how accurately their positions are controlled in relation to the drawing’s references.

What positional tolerancing means in practice

In general technical use, positional tolerancing limits how far a feature may deviate from its theoretically exact location. This matters because assemblies depend on alignment, fit and functional location as much as they depend on nominal dimensions. Within the geometrical tolerancing framework, position is considered separately from form and orientation, since the key concern is the location of the feature relative to specified datums rather than its size alone.

According to the scope given for this edition, the standard covers the principles of positional tolerancing for the locations of geometric elements and provides formulas for calculating suitable tolerance values for mating components. That means the document is concerned with how positional tolerance is interpreted and with the mathematical relationships used when selecting appropriate tolerance magnitudes for assembled parts. Datum structure, feature definition on the drawing, and the functional effect of a tolerance chain are central concepts for understanding this subject.

• Positional tolerancing controls the permitted deviation of a feature from its ideal location.
• Tolerance selection for mating parts is important for assembly fit and functional relationships.
• Geometrical tolerancing complements dimensional size control by addressing location and relationship accuracy.
• This standard addresses the principles of positional tolerancing and formulas for calculating suitable values.