Tolerance Iso 2768 Mk Pdf !full! May 2026

ISO 2768 is the international standard for general tolerances, designed to simplify engineering drawings by providing standardized limits for dimensions without individual tolerance markings . When you see ISO 2768-mK

on a drawing, it specifically combines two different parts of the standard: m (Medium) : Refers to ISO 2768-1 , covering linear and angular dimensions. : Refers to ISO 2768-2

, covering geometrical tolerances such as flatness, straightness, and symmetry. Key Reference Resources (PDF & Articles) Comprehensive Overviews ISO 2768-1 Official Summary

provides the fundamental concepts and tables for linear dimensions. Technical Breakdown Fictiv's Guide to ISO 2768

explains why this standard is used in CNC machining to reduce costs and prevent misunderstandings. Geometric Tolerances : For details on the "K" part (geometry), this ISO 2768-2 Sample iTeh Standards outlines rules for parallelism, perpendicularity, and more. Quick Reference Charts : A widely used General Tolerances Chart PDF ZEISS Quality Forum

provides a one-page lookup for "m" (medium) and other classes. Summary Tables for ISO 2768-mK

These values apply to dimensions where no specific tolerance is listed. waterson.com Part 1: Linear Dimensions (Class m) Nominal Size Range (mm) Tolerance (± mm) Over 3 to 6 Over 6 to 30 Over 30 to 120 Over 120 to 400 Part 2: Geometrical Tolerances (Class K) Nominal Length Range (mm) Straightness/Flatness (mm) Perpendicularity (mm) Symmetry (mm) 100 to 300 (Part 2) or tips on how to properly indicate these on your drawings Quality Assurance Auditor CNC Machinist General Tolerance - ISO 2768 1 & 2 - ZEISS Quality Forum

ISO 2768-mK is an international standard used to simplify engineering drawings by providing general tolerances for dimensions that don't have individual tolerance markings Tolerance Iso 2768 Mk Pdf

. It is widely used in CNC machining for both metals and plastics. The "mK" designation combines two parts of the standard: m (Medium)

: Refers to general tolerances for linear and angular dimensions (Part 1). K (Class K)

: Refers to geometrical tolerances, such as straightness and flatness (Part 2). Key Tolerance Tables for "mK" 1. Linear Dimensions (Class m)

These tolerances apply to lengths, external sizes, and internal sizes. ISO - International Organization for Standardization Nominal Size (mm) Tolerance (± mm) Over 3 to 6 Over 6 to 30 Over 30 to 120 Over 120 to 400 Over 400 to 1000 2. Geometric Tolerances (Class K)

These define the allowed deviation for features like straightness, flatness, and perpendicularity. Nominal Length (mm) Straightness/Flatness (mm) Perpendicularity (mm) 100 to 300 300 to 1000 Where to Find PDF Guides

While the full official standards must be purchased from the

, many manufacturers provide condensed "cheat sheet" PDFs for free: Fictiv ISO 2768 Guide : A clear breakdown of classes and applications. LEADRP General Tolerance Blog : Detailed explanations of the "mK" specific classes. 3ERP Machining Standards ISO 2768 is the international standard for general

: Focuses on practical application in machining and common pitfalls. tolerances or the requirements for Class K?

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

ISO 2768-mK is an international manufacturing standard used to define general tolerances for mechanical parts, specifically for dimensions that don't have individual tolerance callouts on a drawing. Using this standard simplifies technical drawings by removing the need to label every single dimension with a plus/minus value. Breaking Down "mK"

The designation "mK" combines two specific tolerance classes from different parts of the ISO 2768 standard: m (Medium) : Defined in ISO 2768-1 , this class specifies permissible deviations for linear and angular dimensions (like lengths, radii, and diameters). K (Geometric) : Defined in ISO 2768-2 , this class specifies tolerances for geometrical features

such as flatness, straightness, perpendicularity, and run-out. Key Tolerance Tables

The following tables outline the permissible deviations (in mm) for the "m" and "K" classes. Linear Dimensions (Class m)

For basic sizes from 0.5mm up to 4000mm, these are the standard deviations for the medium (m) class: Nominal Length (mm) Permissible Deviation (± 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 Geometrical Tolerances (Class K) Does Not Apply to Everything: The standard explicitly

These deviations apply to the form and position of features under the "K" designation: Feature Type Tolerance Range (mm) Straightness/Flatness 0.05 (up to 10mm) to 0.8 (over 1000mm) Perpendicularity 0.4 (up to 100mm) to 0.8 (over 1000mm) 0.6 (up to 100mm) to 1.0 (over 1000mm) Circular Run-out 0.2 (fixed value) Why Use ISO 2768-mK?

What is ISO 2768? | CNC Machining Tolerance Standards - Fictiv

5. Important Caveats

While useful, ISO 2768-mK has limitations that engineers must understand:

Does Not Apply to Everything: The standard explicitly states that it does not apply to:
- Reference dimensions (shown in brackets).
- Theoretically exact dimensions (boxed dimensions used for GD&T profiles).
- Dimensions that are already governed by other specific standards (e.g., standard fit tolerances like H7/g6).
Plastic and Rubber Parts: ISO 2768 is intended primarily for machined metal parts. Plastics often shrink or warp; ISO 2768-f (Fine) or ISO 2768-c (Coarse) might be more appropriate depending on the material properties, or a material-specific standard may be required.
Responsibility: If a part fails because a non-toleranced dimension was out of spec, the manufacturer is generally not responsible if the part falls within the ISO 2768-mK range. The designer accepts responsibility by selecting this standard in the title block.

2. Scope – What ISO 2768-mK Covers

| Dimension Type | Applies To | |---------------|-------------| | Linear dimensions (mm) | Lengths, widths, heights, diameters, radii, chamfers | | Angular dimensions (°/') | Angles, unless otherwise specified | | Geometric tolerances | Straightness, flatness, circularity, cylindricity, parallelism, perpendicularity, symmetry, runout |

3. Quality Control Efficiency

The standard helps differentiate between "critical" and "non-critical" dimensions. Dimensions that require tighter control than the general standard must be explicitly highlighted on the drawing. This tells the Quality Control (QC) inspector exactly which features require special attention, streamlining the inspection process.

Decoding "MK" in ISO 2768

The keyword "ISO 2768 MK" refers to a specific combination of tolerance classes from the two parts of the standard.

The 'M' (from Part 1): This refers to the "Medium" tolerance class for linear and angular dimensions. ISO 2768-1 defines four classes: f (Fine), m (Medium) , c (Coarse), and v (Very coarse). Medium is the default for most standard machining operations (milling, turning).
The 'K' (from Part 2): This refers to the "K" tolerance class for geometrical tolerances (form and position). ISO 2768-2 defines three classes: H, K , and L.

Therefore, "ISO 2768 MK" means:

General linear tolerances follow the Medium (m) class.
General geometrical tolerances (flatness, straightness, perpendicularity, symmetry, runout) follow the K class.

Breaking Down the Code: "mK"

The code ISO 2768-mK is a shorthand instruction to the workshop and quality control. It consists of two independent specifications:

The "m" (Medium): Refers to the Linear and Angular Tolerance Class from ISO 2768-1. The classes range from fine (f) to very coarse (v). "m" (Medium) is the industry default for standard machining.
The "K" (Klasse): Refers to the Geometrical Tolerance Class from ISO 2768-2. "K" is the standard class for general geometrical tolerances (e.g., straightness, flatness).

In short: Linear dimensions follow "Medium" tolerances; Geometrical features follow "Class K" tolerances.