Part 1 establishes general tolerances for linear dimensions (e.g., lengths, widths, diameters) and angular dimensions (e.g., angles). The standard simplifies drawing notation by allowing the designer to specify a tolerance class in the title block of the drawing rather than next to each dimension.
Mastering Precision: A Deep Dive into ISO 2768 General Tolerances
| Nominal Length Range of Shorter Side (mm) | Fine (f) | Medium (m) | |------------------------------------------:|:--------:|:----------:| | 0 – 10 | ±1° | ±1° | | 10 – 50 | ±0°30' | ±0°30' | | 50 – 120 | ±0°20' | ±0°20' | | 120 – 400 | ±0°10' | ±0°10' | | >400 | ±0°5' | ±0°5' | iso 2768 general tolerances pdf exclusive
The most common industry standard for machined and sheet metal parts is . Table 1: Linear Dimensions (ISO 2768-1, Class m) Nominal Size Range (mm) Tolerance (± mm) 120 to 400 400 to 1000 Table 2: Geometrical Tolerances (ISO 2768-2, Class K) Range (mm) Tolerance (mm) Straightness/Flatness Perpendicularity 100 to 300 How to Draft a "Good" Feature
For most general machining, is the standard used. Nominal Size Range and Tolerance Values (mm) Tolerance Class Over 3-6mm Over 6-30mm Over 30-120mm Over 120-400mm f (fine) m (medium) c (coarse) v (very coarse) Part 1 establishes general tolerances for linear dimensions
The ISO 2768 standard provides application guidelines for various types of dimensions, including:
Engineers and machinists rely on specific tables within the standard to determine the exact numerical values allowed for a given dimension. Linear Dimensions (ISO 2768-1) Table 1: Linear Dimensions (ISO 2768-1, Class m)
Official PDF versions of ISO 2768-1 and ISO 2768-2 are sold exclusively through the ISO store and authorized national standards bodies (such as ANSI, DIN, or BSI). The "exclusivity" refers to the legal right to distribute the content. These documents are often priced as professional tools, which can be a barrier for small businesses, students, and independent engineers.
| Tolerance Class | Short Side Length up to 10mm | 10 to 50mm | 50 to 120mm | 120 to 400mm | >400mm | | :--- | :--- | :--- | :--- | :--- | :--- | | | ±1° | ±0°30' | ±0°20' | ±0°10' | ±0°5' | | m (Medium) | ±1° | ±0°30' | ±0°20' | ±0°10' | ±0°5' | | c (Coarse) | ±1°30' | ±1° | ±0°30' | ±0°15' | ±0°10' | | v (V. Coarse) | ±3° | ±2° | ±1° | ±0°30' | ±0°20' |
Tolerances are selected based on the length of the largest surface or line.