If you’ve seen "ISO 2768-mk" in the title block of a blueprint, What is ISO 2768?
Part 2 focuses on the "form" of the part. There are three classes: H, K, and L. The class is the medium-level requirement for geometry.
The goal is simple: to simplify drawings. By referencing ISO 2768, a designer tells the machinist, "Unless I specify otherwise, follow these standard accuracy levels." Breaking Down the "mk" Suffix general tolerance iso 2768-mk
ISO 2768-mk is a "general" standard. You should never rely on it for: High-precision fits (e.g., H7/g6).
Understanding ISO 2768-mk: The Standard for General Tolerances If you’ve seen "ISO 2768-mk" in the title
It provides a universal language between designers and manufacturers worldwide, ensuring that a part made in Germany fits a part made in the USA. When NOT to use it
ISO 2768-mk is the "Goldilocks" of manufacturing tolerances—not too tight, not too loose. It ensures that parts are functional and interchangeable without unnecessary manufacturing expenses. When you see it on a drawing, you’re looking at a standard of and Medium Geometrical control . The class is the medium-level requirement for geometry
For the 'm' class, the allowable deviation depends on the size of the dimension: Nominal Size (mm) Tolerance (± mm) 120 to 400 400 to 1000 External Radii and Chamfer Heights Nominal Size (mm) Tolerance (± mm) ISO 2768-2: Geometrical Tolerances (The 'k')
Refers to Part 2 of the standard, covering Geometrical tolerances (like flatness, symmetry, and run-out). The 'k' is the class for general geometrical tolerances. ISO 2768-1: Linear Dimensions (The 'm')
For a side up to 100mm, the limit is 0.4mm.