But what exactly is inside this vital standard? How do you interpret its four tolerance classes (f, m, c, v)? And most importantly, where can you download a legitimate, up-to-date ISO 2768 general tolerances PDF?
Essential for any engineering or manufacturing setting, but make sure you are downloading the correct part (Part 1 for linear/angular vs. Part 2 for geometric).
This part controls the form and position of parts. It simplifies geometric dimensioning and tolerancing (GD&T) using three classes: : Fine geometric control. K : Medium geometric control (most widely used). L : Coarse geometric control. ISO 2768-1 Tolerance Tables Linear Dimensions Permissible deviations in millimeters (mm) for basic sizes: Tolerance Class 0.5 to 3mm 30 to 120mm 120 to 400mm 400 to 1000mm f (Fine) m (Medium) c (Coarse) v (Very Coarse) External Radii and Chamfer Heights Permissible deviations in millimeters (mm): Tolerance Class 0.5 to 3mm f (Fine) m (Medium) c (Coarse) v (Very Coarse) Angular Dimensions
"Even if the size is right, is the part straight? Is it round? Class or H would have saved us. Because you left it to the 'General' standard without picking the right class, the machinist followed the law, but the machine failed the mission." The Lesson Learned
Note: Values are in millimeters (mm).
ISO 2768 establishes a system of general tolerance classes to streamline engineering design and manufacturing. Purpose of the Standard
Other common designations include:
The standard defines general tolerances for linear and angular dimensions to simplify technical drawings by removing the need for individual tolerance indications for every feature. It ensures that parts are manufactured within a reasonable accuracy range suitable for most general mechanical engineering purposes. Core Parts of ISO 2768