Here is a conceptual breakdown of what you will find inside the : 1. Linear Dimensions Table (mm) The table cross-references nominal size ranges (e.g., 0.5–3 mm, 3–6 mm, up to 4000 mm) against the three tolerance classes: Fine (f), Medium (m), and Coarse (c).
Because ISO 20457 is a classification standard, its tables do not provide the raw numbers for every single dimension (that is the job of ISO 286, ISO 2768, etc.). Instead, it provides a .
Using the "Medium" class for a 45mm part, the linear tolerance is ± 0.8 mm. This means your part can be 44.2 mm to 45.8 mm.
Unlike specific tolerance standards that apply to one type of feature (like ISO 286 for holes and shafts), ISO 20457 provides a . It helps design engineers and quality managers group parts based on their precision needs.