ISO 2768: A Guide to General Tolerances for Linear and Angular Dimensions
ISO 2768 is an international standard that specifies general tolerances for linear and angular dimensions without individual tolerance indications. It consists of two parts: ISO 2768-1 and ISO 2768-2. In this article, we will focus on ISO 2768-1 and
explain its purpose, scope, and tolerance classes.

Iso 2768 Free Download Pdf
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What is the purpose of ISO 2768-1?
ISO 2768-1 is intended to simplify drawing indications and reduce the number of tolerances that need to be specified individually. It applies to the dimensions of parts that are produced by metal removal or parts that are formed with sheet metal
fabrication. It does not apply to auxiliary dimensions, theoretically exact dimensions, or dimensions that are covered by other standards on general tolerances.

What is the scope of ISO 2768-1?
ISO 2768-1 applies to the following dimensions that do not have an individual tolerance indication:


linear dimensions (e.g. external sizes, internal sizes, step sizes, diameters, radii, distances, external radii, and chamfer heights for broken edges);
angular dimensions, including angular dimensions usually not indicated, e.g. right angles (90°), unless reference to ISO 2768-2 is made, or angles of uniform polygons;
linear and angular dimensions produced by machining assembled parts.

What are the tolerance classes of ISO 2768-1?
ISO 2768-1 specifies four tolerance classes: f (fine), m (medium), c (coarse), and v (very coarse). The tolerance class determines the permissible deviations for the dimensions in question. The tolerance class should be chosen based on the production
capacity of the manufacturer and the requirements of the parts to be made. Usually, ISO 2768-fH is ideal for CNC machining.

The following tables show the tolerance values for each class according to ISO 2768-1[^1^] [^2^]:



Table 1 - Linear Dimensions
Ranges of nominal lengths in mmf (fine)m (medium)c (coarse)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
over 2000 up to 4000--How to indicate ISO 2768-1 on drawings?
If general tolerances in accordance with ISO 2768-1 shall apply, ISO 2768 followed by the tolerance class (e.g. ISO 2768-m) shall be indicated in or near the title block of the drawing. If different tolerance classes are required for different dimensions,
they shall be indicated adjacent to the relevant nominal dimensions.

For example, a drawing with general tolerances of medium class for linear dimensions and coarse class for angular dimensions can be indicated as follows:




Source: CNCLATHING[^2^]

Conclusion
ISO 2768-1 is a useful standard for simplifying drawing indications and specifying general tolerances for linear and angular dimensions. It helps to reduce the number of individual tolerances and facilitate the communication between designers and
manufacturers. It also provides four tolerance classes to suit different production capacities and part requirements.

If you want to download a free PDF file of ISO 2768-1, you can visit one of the following links:


ISO 2768 1 & 2 - ISO General Tolerances Chart (PDF) - DEK[^1^]
General Tolerances DIN ISO 2768 | PDF | Engineering Tolerance ... - Scribd[^3^]

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