ISO 2768 is the international standard used to simplify technical drawings by providing general tolerances for linear and angular dimensions. Without these standards, engineers would have to manually define tolerances for every single part feature, cluttering the design. What is ISO 2768?
ISO 2768 is designed to define the "customary workshop accuracy." By citing "ISO 2768" in a drawing title block, you automatically apply a set of allowable deviations to all dimensions that don't have a specific tolerance listed. Key Benefits Cleaner Drawings: Removes "clutter" from blueprints.
Cost Efficiency: Prevents over-engineering and unnecessary precision.
Consistency: Ensures different machine shops produce similar results. Part 1: ISO 2768-1 (Linear and Angular Dimensions)
This section covers basic dimensions like lengths, radii, and angles. It breaks down into four tolerance classes: f (Fine): For precision instruments. m (Medium): The most common standard for general machining. c (Coarse): For parts where accuracy is less critical. v (Very Coarse): For rough manufacturing processes. Linear Dimensions Table (Commonly used 'm' class) Nominal Size (mm) 120 to 400 Tolerance (±mm) Part 2: ISO 2768-2 (Geometrical Tolerances)
While Part 1 handles "how big" a part is, Part 2 handles "what shape" it is. It focuses on features like flatness, symmetry, and circular run-out. It uses three classes: H, K, and L.
Flatness and Straightness: Limits how much a surface can bow or curve.
Perpendicularity: Ensures two surfaces meet at a true 90-degree angle.
Symmetry: Regulates the alignment of two features relative to a center plane. How to use ISO 2768 in your Project
To apply these rules, you must include a note in your drawing's title block. It usually looks like this: ISO 2768-mk Iso 2768 General Tolerances Pdf
The "m" refers to the Medium class for linear dimensions (Part 1).
The "k" refers to the K class for geometric tolerances (Part 2).
📍 Pro Tip: Always prioritize functional tolerances. If a specific fit (like a bearing bore) requires high precision, manually override the ISO 2768 general tolerance with a specific +/- value. Common Misconceptions
It’s not for plastics: ISO 2768 is technically for metal removal (machining) or sheet metal. Plastic parts usually follow ISO 20457.
It’s not "Law": It only applies if you explicitly state it on your technical drawing.
If you are looking for a specific PDF version to keep on your shop floor, I can help you: Find a summary cheat sheet for your desk Compare it to the American ANSI/ASME standards
Explain how to measure these tolerances using calipers or a CMM
Linear dimensions (ISO 2768-1, class m – medium):
| Nominal size (mm) | Tolerance (± mm) | |------------------|------------------| | 0.5 to 3 | 0.1 | | >3 to 6 | 0.1 | | >6 to 30 | 0.2 | | >30 to 120 | 0.3 | | >120 to 400 | 0.5 | | >400 to 1000 | 0.8 | | >1000 to 2000 | 1.2 | ISO 2768 is the international standard used to
| Field | Example Value |
|-------|----------------|
| Nominal size (mm) | 45 |
| Tolerance class | m (medium) |
| Dimension type | Linear |
| Output format | PDF report (or inline text) |
ISO 2768 is a vital tool for simplifying engineering drawings. By referencing a standard tolerance class (like ISO 2768-mK) in the title block, engineers save time on drafting and clearly communicate the required precision level to the machine shop, ensuring a balance between part quality and production cost.
Disclaimer: This write-up is for educational purposes. For official manufacturing and quality control, always refer to the official ISO 2768 PDF document purchased from an authorized standards body (such as ISO.org or ANSI).
If you are looking for information on ISO 2768 General Tolerances
, here is a breakdown of the standard used to simplify technical drawings by providing universal tolerance classes for dimensions without individual indications. 🛠️ What is ISO 2768?
ISO 2768 is an international standard that defines general tolerance classes for linear and angular dimensions, as well as geometrical features. It is divided into two primary parts: ISO - International Organization for Standardization Part 1 (ISO 2768-1):
Focuses on linear and angular dimensions. It specifies four tolerance classes: (very coarse) Part 2 (ISO 2768-2):
Focuses on geometrical tolerances (GD&T) such as flatness, straightness, and symmetry. It uses three classes: 📄 Why Use General Tolerances? Simplification:
Reduces the number of specific tolerance callouts on a drawing, making it cleaner and easier to read. Efficiency: Example User Input (UI mockup): | Field |
Speeds up the design and manufacturing workflow by providing a "default" accuracy level. Cost-Effective:
Prevents over-engineering by applying appropriate tolerances based on the manufacturing process. 🔍 Resources & Downloads
While the official full-text standard is a paid document, many manufacturers and engineering hubs provide summary tables and PDF guides for reference: Official Standard: You can purchase the current version directly from the ISO 2768-1 Official Page Technical Guides: Sites like
offer detailed breakdowns and charts of the tolerance values for each class. Quick Reference PDF:
For a visual summary of the tolerance tables, you can view this General Tolerance Guide ZEISS Quality Forum specific numerical values
| Nominal Size Range | Class f (Fine) | Class m (Medium) | Class c (Coarse) | Class v (Very Coarse) | | :--- | :--- | :--- | :--- | :--- | | 0.5 up to 3 | ±0.05 | ±0.1 | ±0.2 | — | | Over 3 up to 6 | ±0.05 | ±0.1 | ±0.3 | ±0.5 | | Over 6 up to 30 | ±0.1 | ±0.2 | ±0.5 | ±1.0 | | Over 30 up to 120 | ±0.15 | ±0.3 | ±0.8 | ±1.5 | | Over 120 up to 400 | ±0.2 | ±0.5 | ±1.2 | ±2.5 | | Over 400 up to 1000 | ±0.3 | ±0.8 | ±2.0 | ±4.0 | | Over 1000 up to 2000 | ±0.5 | ±1.2 | ±3.0 | ±6.0 |
Note: For nominal sizes below 0.5 mm, the deviations shall be indicated directly next to the nominal dimension.
ISO 2768 defines general tolerances for linear and angular dimensions and for geometrical tolerances where specific tolerances are not indicated on technical drawings. This paper summarizes the standard’s scope, tolerance classes, application principles, interpretation for production and inspection, examples, and guidance for creating clear engineering drawings. It also lists recommended references and notes on accessing the official PDF.