Despite its utility, ISO 2768 is frequently misunderstood. Some engineers assume that invoking the standard excuses them from thinking about fits. This is a dangerous fallacy. The general tolerance applies only to dimensions where the feature’s function is not compromised by the default range. For press fits, bearing seats, or sliding interfaces, ISO 2768 is wholly inadequate—these require explicit tolerances (e.g., H7/g6). Furthermore, the PDF’s second part (ISO 2768-2) addresses geometrical tolerances like straightness and flatness, which many novices overlook. Relying solely on the linear tolerances while ignoring the geometric ones is a recipe for assembly failure, especially for welded or bent sheet metal parts.

Looking for the official standard? Purchase the original PDF from the ISO store or your local standards body (ANSI, BSI, DIN) to ensure you have the legally binding document. Use this guide for daily reference.

General runout tolerance is always equal to the general tolerance for flatness (for cylindrical parts) or the larger of the two: flatness or perpendicularity.

The ISO 2768 standard plays a crucial role in ensuring the accuracy and interchangeability of manufactured parts and products. The standard provides several benefits, including: