What are general tolerances according to ISO 2768?
Definition and significance of ISO 2768
ISO 2768 is an international standard that defines the permissible deviations in dimensional, form and position tolerances. General tolerances are particularly important for components where a certain dimensional deviation is technically uncritical. This simplifies the production process, reduces costs and at the same time improves quality assurance.
Calculating general tolerances: interactive tolerance calculator according to DIN ISO 2768
Toleranzrechner nach DIN ISO 2768-1
Dieser Toleranzrechner basiert auf den geprüften Werten der DIN ISO 2768-1.
Difference between ISO 2768 and DIN ISO 2768
While the designation DIN ISO 2768 refers to the German version of the international standard, ISO 2768 is the original international version. In content, both are identical.
Areas of application for general tolerances
ISO 2768 is applied in metalworking, mechanical engineering and wherever technical drawings are created. It simplifies dimensioning because a specific tolerance does not have to be specified for each dimension.
How is the ISO 2768 standard structured?
The standard is divided into two parts:
ISO 2768-1: Tolerances for length and angular dimensions
This part governs tolerances for linear dimensions (for example lengths, widths) and angular dimensions. Tolerances depend on the nominal size range and are divided into four classes:
- f (fine)
- m (medium)
- c (coarse)
- v (very coarse)
Depending on the application and the desired precision, the appropriate tolerance class is selected.
ISO 2768-2: Geometric tolerances
This section defines tolerances for geometric properties such as straightness, flatness, roundness and position.
Which tolerance classes exist in ISO 2768?
Overview of tolerance classes for length dimensions
| Nominal size range (mm) | f (fine) | m (medium) | c (coarse) | v (very coarse) |
|---|---|---|---|---|
| 0.5 to 3 | ±0.05 | ±0.1 | ±0.2 | - |
| over 3 to 6 | ±0.05 | ±0.1 | ±0.3 | ±0.5 |
| over 6 to 30 | ±0.1 | ±0.2 | ±0.5 | ±1.0 |
| over 30 to 120 | ±0.15 | ±0.3 | ±0.8 | ±1.5 |
| over 120 to 400 | ±0.2 | ±0.5 | ±1.2 | ±2.5 |
| over 400 to 1000 | ±0.3 | ±0.8 | ±2.0 | ±4.0 |
| over 1000 to 2000 | ±0.5 | ±1.2 | ±3.0 | ±6.0 |
Selecting the right tolerance class
The choice of tolerance class depends on the function of the component. For precision parts, class f (fine) is preferred, while for standard components class m (medium) is usually sufficient.
How are tolerances according to ISO 2768 indicated in technical drawings?
Correct specification of general tolerances
General tolerances are indicated in technical drawings by a note such as: General tolerances according to DIN ISO 2768-mK
Here:
- m stands for the tolerance class of dimensional deviation
- K stands for geometric tolerances (for example straightness, flatness)
Examples of tolerance specifications in drawings
A typical note in a drawing reads: Dimensions in mm. Tolerances according to DIN ISO 2768-mK.
What is the difference between ISO 2768 and the new ISO 22081?
Development of ISO 22081
ISO 22081 is the new international standard that applies specifically to general geometric tolerances. It extends the definitions of ISO 2768 and provides a more detailed basis for specifying tolerances.
Main differences from ISO 2768
The key difference lies in the more detailed definition of geometric tolerances. While ISO 2768 establishes general rules for dimensional and form tolerances, ISO 22081 goes a step further and defines more specific requirements.
How are the tolerance tables according to ISO 2768 applied in practice?
Step-by-step guide
- Check the drawing: are there specific tolerance specifications? If not, the general tolerances apply.
- Determine the nominal size: what is the dimension of the component?
- Select the tolerance class: depending on the precision requirement.
- Read the permissible deviation: from the tolerance table.
Avoiding common errors in application
- Uncertainty about the correct tolerance class
- Disregard of special requirements for form and position tolerances
- Incorrect transfer of tolerances onto manufacturing drawings
Which advantages does the use of general tolerances according to ISO 2768 offer?
- Efficiency gains in design: the simplification of tolerance specifications reduces the working time of designers.
- Cost reduction: appropriate tolerance allocation prevents unnecessarily tight dimensional requirements, reducing production costs.
- Simplification of manufacturing and quality control: standardised tolerances simplify the production and final inspection of components.
GOBA Takeaway: Why is ISO 2768 so important?
ISO 2768 is an indispensable tool in mechanical engineering and manufacturing. It ensures a uniform definition of tolerances, simplifies technical communication and contributes to cost optimisation. For designers and production engineers, knowledge of this standard is essential for developing high-quality and economical components.
GOBA manufactures stamped and bent parts as well as custom products reliably to DIN ISO 2768.