ISO 2768

The standard defines general tolerances for linear and angular dimensions, as well as geometric characteristics, to simplify engineering drawings and manufacturing processes. It ensures that parts can be produced with "customary workshop accuracy" without requiring a specific tolerance for every individual dimension. Structure of ISO 2768 The standard is divided into two primary parts:

Streamlined QC:

Quality control teams know exactly what to inspect without searching for individual callouts on every feature. Structure of the Standard: Part 1 and Part 2

For linear dimensions, there are four tolerance classes. If a drawing applies this standard, it must be indicated near the title block (e.g., ISO 2768-m Class Designation Description Recommended Usage Precision machining General machining (most common) Casting or rough fabrication Very Coarse Large, non-critical parts Common Linear Tolerance Values (mm) Deviations depend on the nominal length of the feature: 0.5 to 3 mm: plus or minus 0.05 plus or minus 0.1 3 to 6 mm: plus or minus 0.05 plus or minus 0.1 30 to 120 mm: plus or minus 0.15 plus or minus 0.3 400 to 1000 mm: plus or minus 0.3 plus or minus 0.8 Reference Resources (PDF Guides)

1. The "No-Dimension" Shortcut: The best feature of this PDF is how it simplifies drawings. Instead of cluttering a blueprint with individual tolerances for every chamfer, radius, or non-critical hole, you simply write “ISO 2768-m” in the title block. This PDF acts as the decoder ring, saving hours of drafting time.
2. Four Clear Classes: The standard’s breakdown into f (fine), m (medium), c (coarse), and v (very coarse) is brilliantly practical. A good PDF summary clearly shows that a 100mm part with "medium" tolerance allows ±0.3mm, while "fine" requires ±0.15mm. This helps junior engineers avoid over-tolerancing expensive parts.
3. Geometric (Part 2) Coverage: The better PDFs don't stop at linear sizes. They include the straightness and flatness tables. Seeing that a "Medium" class allows 0.5mm per 100mm of flatness immediately prevents arguments with quality control.
4. Portable Reference: Having this as a PDF (on your phone, laptop, or shop tablet) beats flipping through the $200+ official standard document. The summarized charts are 90% of what you need, 100% of the time.

2. Standard Structure

ISO 2768 is designed to simplify technical drawings by specifying general tolerances for dimensions and features without individual tolerance indications. This ensures that the "customary workshop accuracy" is maintained for non-critical features, reducing drawing complexity and streamlining production. The standard is divided into two primary parts: