General Tolerance Iso 2768-mk May 2026

ISO 2768‑1 defines general tolerances for linear and angular dimensions on drawings when no specific tolerance is given. "m" = medium tolerance class; "k" = coarse for form and position? — ISO 2768 uses two parts: Part 1 (general tolerances — linear/angular) with tolerance classes f (fine), m (medium), c (coarse), v (very coarse); Part 2 (geometrical tolerances — form and position) with symbols for tolerances (no separate k). Here “mk” likely means linear class m and unspecified geometric class (commonly k is not part of ISO 2768 — confirm in standard).

Applies to flatness, straightness, perpendicularity, symmetry, and circular runout.

| Nominal Size Range (mm) | Flatness / Straightness (mm) | Perpendicularity (mm) | Symmetry (mm) | Circular Runout (mm) | | :--- | :--- | :--- | :--- | :--- | | 0.5 to 10 | 0.05 | 0.1 | 0.5 | 0.1 | | >10 to 30 | 0.1 | 0.2 | 0.5 | 0.1 | | >30 to 100 | 0.1 | 0.3 | 0.5 | 0.1 | | >100 to 300 | 0.2 | 0.4 | 0.5 | 0.1 | | >300 to 1000 | 0.3 | 0.5 | 0.5 | 0.1 | | >1000 to 3000 | 0.4 | 0.6 | 0.5 | 0.1 |

Important: For parallelism, the tolerance equals the value of the size tolerance. For positional tolerances, the standard recommends using ISO 2768-2 only for "non-functional" features; otherwise, individually specify.

The first letter refers to ISO 2768-1 (Linear & Angular tolerances). There are four classes:

Example of ‘m’ class (for metric sizes): For a nominal size between 6mm and 30mm, the ‘m’ tolerance is ±0.2mm. For 120mm to 400mm, it is ±0.5mm.

| Geometrical Character | Nominal Size Range (mm) | Tolerance (mm) | | :--- | :--- | :--- | | Straightness & Flatness | Up to 10 | 0.05 | | | Over 10 up to 30 | 0.1 | | | Over 30 up to 100 | 0.2 | | | Over 100 up to 300 | 0.4 | | | Over 300 up to 1000 | 0.6 | | Perpendicularity | Up to 100 | 0.4 | | | Over 100 up to 300 | 0.6 | | | Over 300 up to 1000 | 0.8 | | Symmetry | Up to 100 | 0.6 | | | Over 100 up to 300 | 0.8 | | | Over 300 up to 1000 | 1.0 | | Run-out (Circular) | Any length | 0.3 |

Note: According to ISO 2768-2, general tolerances for cylindricity are not specified; the tolerance is deemed to be equal to the tolerance for circularity (run-out). general tolerance iso 2768-mk

ISO 2768-2 does not define a general tolerance for cylindricity. If cylindricity is critical, it must be specifically indicated on the drawing using GD&T symbols (⌭).

The second letter refers to ISO 2768-2 (Geometric tolerances). The classes are H, K, L.

Example of ‘k’ class:

ISO 2768-mk provides a cost-effective, industry-standard default tolerance for machined parts where precision is not critical. It balances manufacturing ease with acceptable quality. However, engineers must explicitly specify tighter tolerances for mating, safety, or high-precision features. This report shall be appended to the company’s quality management system (QMS) as the reference for general tolerance compliance.

Approved by:

[Name], Lead Engineer
Date: ___________

This report outlines the application and specifications of the ISO 2768-mK general tolerance standard, which is widely used in mechanical engineering to simplify technical drawings by providing standard tolerances for dimensions and geometric features that do not have individual callouts. 1. Scope and Application ISO 2768‑1 defines general tolerances for linear and

ISO 2768-mK is an international standard that defines general tolerances for machining processes, such as CNC machining. It is typically indicated in the drawing's title block as "General Tolerance: ISO 2768-mK".

ISO 2768-1 (m): Represents the "medium" tolerance class for linear and angular dimensions (external sizes, diameters, radii, distances).

ISO 2768-2 (K): Specifies general geometric tolerances, primarily for flatness, straightness, parallelism, and symmetry. 2. Tolerance Class "m" (Linear & Angular)

The "m" (medium) class is the most common choice for metal parts. It sets permissible deviations based on the nominal size of the dimension: Nominal Size (mm) Tolerance (± mm) Over 3 to 6 Over 6 to 30 Over 30 to 120 Over 120 to 4000 0.5 to 2.0 (variable) Data sourced from LEADRP and ZEISS Quality Forum. 3. Tolerance Class "K" (Geometric)

The "K" class defines general limits for the form and position of features. For example, surfaces with fitting dimensions must remain flat and parallel within the specified K-class range to ensure assembly functionality. 4. Technical Advantages

Simplification: Reduces drawing complexity by eliminating the need to label every single dimension with a specific tolerance.

Cost Efficiency: Using a standard "medium" tolerance helps avoid unnecessarily tight specifications that drive up manufacturing costs. Important: For parallelism , the tolerance equals the

Consistency: Provides a baseline for quality inspection across different suppliers and manufacturing facilities. General Tolerance - ISO 2768 1 & 2 - ZEISS Quality Forum

A feature for ISO 2768-mk establishes a "medium" precision standard for parts, ensuring they are manufactured within acceptable limits for both size and shape without requiring individual tolerance callouts for every dimension. The designation breaks down into two parts:

m (Medium): Governed by ISO 2768-1, this defines permissible deviations for linear and angular dimensions, such as lengths, radii, and chamfers.

k (Class K): Governed by ISO 2768-2, this covers geometric characteristics like flatness, straightness, and circular runout. Tolerance Tables for ISO 2768-mk

The following values apply based on the nominal size of the feature: Linear Dimensions (Class m)

For linear measurements like external/internal sizes, heights, and distances. Nominal Range (mm) Tolerance (± mm) 120 to 400 400 to 1000 Geometric Tolerances (Class K)

For shape and position characteristics without individual indications. Feature Type Range (mm) Tolerance (mm) Straightness/Flatness 100 to 300 Perpendicularity Symmetry Run-out (Circular) All ranges Key Implementation Details

The Basics Of General Tolerance Standard - ISO 2768-mK - LEADRP

| Shorter side length range | Tolerance (mm) | |----------------------------|----------------| | ≤ 100 | 0.2 | | >100 – 300 | 0.3 | | >300 – 1000 | 0.4 | | >1000 – 3000 | 0.5 |