TS ISO 10578

TS ISO 10578 addresses projected tolerance zones in technical drawings, focusing on how this kind of geometric tolerance is defined and how it is indicated on the drawing. In practice, this concept belongs to the broader language of orientation and location tolerancing, where the controlled feature must remain acceptable not only at the surface but over an extended functional height or depth.

What a projected tolerance zone means in engineering terms

In general technical use, a projected tolerance zone extends the effect of the tolerance beyond the part surface for a specified distance. This matters for features such as holes, pins, axes and other cylindrical or linear features when assembly performance depends on the feature’s usable projection rather than only its surface opening. The standard’s subject is the method of indicating that concept on the drawing; it does not, from the provided scope, set product-specific design values or application limits.

Why the drawing notation matters

In geometric tolerancing, the way a requirement is shown is as important as the requirement itself, because design, manufacturing and inspection must interpret it consistently. A projected tolerance zone notation makes it clear that the tolerance applies to an extended functional region, not just to a local surface boundary. That helps distinguish projected control from ordinary surface-limited tolerance zones and supports more reliable communication where alignment or engagement depends on the full working length of a feature.

• The standard defines the method for tolerancing by indication of a projected tolerance zone.
• It specifies the way this indication is shown on technical drawings.
• It is relevant to orientation and location tolerancing in general engineering practice.
• It helps express control over the functional extension of a feature beyond the surface.