The Basics of General Tolerance Standard – ISO 2768

Every feature on products or parts has a size and a geometrical shape. To ensure that the size and geometry of all features are made as required, SMT carefully takes care of the tolerancing on the drawing. Nothing shall be implied or left to interpretation in the workshop or inspection department. SMT General Tolerances for size and geometry make it easier to ensure that the size and geometry of all features can be done as requested.

What is ISO 2768 ?

The ISO 2768 series of standards were developed by the International Organization for Standardization to provide general tolerances for linear and angular dimensions without individual tolerance indications on technical drawings. Since individual tolerances aren’t provided, the designer must ensure that products made to the drawings will function properly.

General Tolerances ISO 2768

ISO 2768-1 stand for the general tolerances for linear and angular dimensions without individual tolerance indications, ISO 2768-1 indicates the linear dimensions and angular dimensions such as external sizes, internal sizes, step sizes, diameters, radii, distances, external radii, and chamfer heights for broken edges. This standard covers general tolerances in three 4 classes of tolerance:

• m – Medium tolerances
• f – Fine tolerances
• c – Coarse tolerances
• v – Very coarse tolerances

Table 1 – Linear Dimensions

Table 2 – External Radii and Chamfer Heights

Table 3 – Angular Dimensions