The designation "mk" consists of two distinct accuracy grades: 1. The "m" (Medium) – Linear Dimensions

Implementing ISO 2768-mk provides substantial advantages to design teams and manufacturing facilities alike: : Eliminates the need to write ±plus or minus

Angular deviations are scaled based on the length of the shorter leg of the angle being measured. Length of Shorter Leg (mm) Permissible Deviations for Class m Over 10 to 50 Over 50 to 120 Over 120 to 400 Table 4: Geometrical Tolerances (Class K)

Table 2: Permissible Deviations for Broken Edges (External Radii and Chamfers)

While MK is the industry workhorse, it is not universal. Do not use ISO 2768 MK if:

In the world of technical drawing and precision manufacturing, communication is everything. A single missing decimal point or an incorrectly assumed tolerance can lead to scrapped parts, costly rework, and delayed projects. This is where becomes the silent guardian of global engineering.

These apply to the shape and position of features without individual GD&T callouts. Up to 100mm 100–300mm 300–1000mm 1000–3000mm Perpendicularity Symmetry Circular Run-out Sources: Runsom PDF , Fictiv . Angular Dimensions (Class "m") Nominal Length (Short Side) up to 10 mm 10 to 50 mm 50 to 120 mm 120 to 400 mm over 400 mm Sources: Xometry, RpProto. Usage & Standards Understanding ISO 2768-mK Tolerances for Engineers

For dimensions below 0.5 mm, the deviations must be indicated directly on the drawing. Similar tables exist for angular dimensions and for external radii and chamfer heights.

: One of three geometrical tolerance classes (H, K, and L). Class K is the intermediate precision level.

To legally and technically bind a manufacturer to these guidelines, the standard must be stated explicitly inside or near the drawing title block.

| Nominal Length Range (mm) | f (Fine) | | c (Coarse) | v (Very Coarse) | | :--- | :--- | :--- | :--- | :--- | | 0.5 up to 3 | ±0.05 | ±0.1 | ±0.2 | – | | over 3 up to 6 | ±0.05 | ±0.1 | ±0.3 | ±0.5 | | over 6 up to 30 | ±0.1 | ±0.2 | ±0.5 | ±1.0 | | over 30 up to 120 | ±0.15 | ±0.3 | ±0.8 | ±1.5 | | over 120 up to 400 | ±0.2 | ±0.5 | ±1.2 | ±2.5 | | over 400 up to 1000 | ±0.3 | ±0.8 | ±2.0 | ±4.0 | | over 1000 up to 2000 | ±0.5 | ±1.2 | ±3.0 | ±6.0 | | over 2000 up to 4000 | – | ±2.0 | ±4.0 | ±8.0 |

Alternatively: for general angle dimensions.

This comprehensive guide breaks down what ISO 2768-mk means, provides the exact tolerance tables you need, explains how to interpret it on a blueprint, and highlights why downloading an reference sheet is essential for your engineering workflow. What Does "ISO 2768-mk" Stand For?

It is important to note that ISO 2768 is not a universal standard. It is most common in Europe and Asia. In the United States, the dominant standard for general tolerances is often implied by the number of decimal places on a dimension per ASME Y14.5.

ISO 2768 is an international standard that provides general geometric and dimensional tolerances for parts produced by metal removal (machining) or sheet metal fabrication. It simplifies technical drawings by establishing a set of standard allowable variations for dimensions that do not have specifically indicated tolerances. The standard is divided into two distinct parts:

These tolerances apply to nominal sizes such as external sizes, internal sizes, steps, diameters, and radii. All values are in millimeters (mm). Nominal Size Range (mm) Permissible Deviations for Class m (mm) Over 3 to 6 Over 6 to 30 Over 30 to 120 Over 120 to 400 Over 400 to 1000 Over 1000 to 2000 Over 2000 to 4000 Table 2: Broken Edges (External Radii and Chamfer Heights)

Part 2 defines three classes: , K , and L . These control the shape and position of features without individual callouts.