Instead of detailing thousands of microscopic tolerances on every dimension line—which causes visual clutter—design engineers can apply a single rule in the title block: ISO 2768-mk . This tells the machinist that any unmarked dimensions default to these standard boundaries. Cost-Effective Production
If you are referencing an ISO 2768-mK PDF, you will typically utilize look-up tables. Here is a simplified example of how linear tolerances work under class "m":
refers to Part 2 (Geometrical tolerances) and stands for the Medium-tight geometrical class.
: For a nominal length of 30mm to 120mm, the "m" class allows a deviation of 2. ISO 2768-2 (Part 2): The "K" Class This part focuses on geometrical tolerances
These define the allowed error in degrees and minutes for angles, also scaled based on the length of the shorter leg of the angle. Tolerance Iso 2768 Mk Pdf
tolerances next to every single dimension. The drawing remains legible and easy to interpret.
Using "mK" for large, non-functional parts can drive up costs unnecessarily, while using it for delicate assemblies might result in poor fits.
For technical implementation, you can find detailed tolerance tables and PDF charts from manufacturing experts like
: Instead of memorizing numerical values or flipping through thick engineering manuals, a single-page PDF chart allows quick cross-referencing during the design or inspection phase. Instead of detailing thousands of microscopic tolerances on
Under ISO 2768-2, if a drawing uses the "K" class, the general runout tolerance is equal to the general tolerance for diameter (from the M class) but capped typically at the K class values.
This article provides a comprehensive overview of what ISO 2768-mK entails, how to interpret the code, and why it is essential for modern production.
Table 1: Permissible Deviations for Linear Dimensions (Except Broken Edges)
Conclusion ISO 2768 offers a pragmatic balance between design clarity and manufacturing economy by supplying default tolerances for non-critical dimensions. Correctly applied, it reduces documentation effort and production cost while maintaining acceptable interchangeability. However, designers must judiciously identify critical features and specify explicit tolerances when function, safety, or assembly demands higher precision. In contemporary practice, ISO 2768 complements, rather than replaces, more detailed tolerancing systems like GD&T, forming part of an overall strategy to communicate design intent efficiently and economically. Here is a simplified example of how linear
This part applies to external and internal sizes, diameters, radii, and distances. The permissible deviation (±) depends on the nominal length of the feature: Nominal Length (mm) Medium (m) Class (± mm) over 3 to 6 over 6 to 30 over 30 to 120 over 120 to 400 over 400 to 1000 Data source: ZEISS Quality Forum and Eurotools . 3. ISO 2768-2: Geometrical Tolerances ("K")
Geometrical Tolerances: Perpendicularity and Symmetry (Class K)
To properly apply ISO 2768-mk to a design, engineers and machinists reference standardized tables. Below are the precise values required for the and K designations. Table 1: Linear Dimensions (Class m)
Note: While many third-party manufacturing websites offer free summary charts via PDF download, formal compliance audits require referencing official standards documents purchased directly through the ISO Store or national standards bodies like ANSI or DIN.
