ISO 2768 Tolerance Standards for CNC Machined Parts
ISO 2768 defines general tolerances for linear dimensions, angular dimensions, and geometrical features that do not have individual tolerance annotations on engineering drawings.
Engineering Specifications & Parameters
Benefit
Simplifies CAD drawings by establishing baseline tolerances
Drawing Annotation
e.g. ISO 2768-mK
Standard CNC Class
ISO 2768-m (Medium) or ISO 2768-f (Fine)
Standard Designation
ISO 2768-1 (Linear/Angular) & ISO 2768-2 (Geometrical)
ISO 2768 Classes
ISO 2768-f (Fine): Precision components, watchmaking, high-accuracy robotics.
ISO 2768-m (Medium): Global standard default for general CNC machining.
ISO 2768-c (Coarse): Sheet metal, stamping, raw stock.
ISO 2768-m Linear Dimensions Table
0.5 to 3 mm: $\pm 0.1$ mm
>3 to 6 mm: $\pm 0.1$ mm
>6 to 30 mm: $\pm 0.2$ mm
>30 to 120 mm: $\pm 0.3$ mm
>120 to 400 mm: $\pm 0.5$ mm
Frequently Asked Questions
What does ISO 2768-mK mean on a drawing title block?
The 'm' denotes medium linear/angular tolerance (Part 1), and 'K' denotes general geometrical flatness/straightness tolerance (Part 2).
