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')
Design engineers do not have to calculate custom tolerances for every single hole, chamfer, and slot.
For a length up to 100mm, the 'k' class allows a 0.2mm deviation.
The lowercase letter represents the tolerance class for linear dimensions (lengths, radii, diameters) and angular dimensions. ISO 2768-1 defines four accuracy classes: f – Fine m – Medium c – Coarse v – Very Coarse general tolerance iso 2768-mk
For standard linear measurements like length or diameter, the permissible deviation increases as the part gets larger. Nominal Length Range (mm) Tolerance (± mm) 120 to 400 Source: Derived from General Tolerances ISO 2768-1 Geometrical Tolerances (ISO 2768-K)
, such as external sizes, internal sizes, radii, and chamfer heights. ISO 2768-2 . It governs geometrical tolerances
The notation "mK" combines two distinct parts of the standard: Refers to Part 2 of the standard, covering
The standard represents the "Medium" standard of modern manufacturing. It balances manufacturing cost with functional reliability. By applying this standard, companies reduce drawing clutter, minimize misinterpretation, and ensure that parts are manufactured to a consistent, acceptable quality level.
Angular tolerances apply to the length of the shorter leg of the angle.
Geometrical tolerances ensure the shape and position of features remain within acceptable limits. Straightness and Flatness: For a length up to 100mm, the 'k' class allows a 0
The purpose of general tolerances is to define the permissible deviation for dimensions that are not individually indicated on the drawing. These tolerances represent the normal manufacturing accuracy achievable by standard workshop machinery.
Instead of writing ± values for every single hole or edge, one note covers everything non-critical.
Symmetry tolerances ensure that features sharing a common central plane are properly balanced: Nominal Length Range (mm) Symmetry Tolerance (mm) Run-Out (Circular Run-Out)
The designation combines two separate parts of the ISO 2768 standard: