For linear dimensions, there are four tolerance classes. If a drawing applies this standard, it must be indicated near the title block (e.g., ISO 2768-m Class Designation Description Recommended Usage Precision machining General machining (most common) Casting or rough fabrication Very Coarse Large, non-critical parts Common Linear Tolerance Values (mm) Deviations depend on the nominal length of the feature: 0.5 to 3 mm: plus or minus 0.05 plus or minus 0.1 3 to 6 mm: plus or minus 0.05 plus or minus 0.1 30 to 120 mm: plus or minus 0.15 plus or minus 0.3 400 to 1000 mm: plus or minus 0.3 plus or minus 0.8 Reference Resources (PDF Guides)
Other combinations include: ISO 2768-fH (Fine/Precise), ISO 2768-cL (Coarse/Coarse). Iso 2768 General Tolerances Pdf
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The Zeiss ISO 2768-2 PDF shows that these tolerances depend on the length of the feature being measured:
Often, a drawing will reference a combined tolerance, such as . Here, the "m" refers to the medium tolerance class for linear and angular dimensions from ISO 2768-1, while the "K" denotes the medium class for geometrical tolerances from ISO 2768-2. This notation efficiently communicates the default precision requirements for the entire part.