Iso 2768-mh Tolerance Chart May 2026

The existence of this chart does not mean you should never add explicit tolerances.

Do not use ISO 2768-mh for:

Next time you see that title block, you’ll know exactly what margin of error the shop floor is working with.

#Engineering #MechanicalDesign #ISO2768 #GD&T #Manufacturing #TechnicalDrawing

In the world of mechanical engineering, ISO 2768-mH is the "silent guardian" of technical drawings. It’s a standard that ensures parts fit together without requiring an engineer to painstakingly label every single minor dimension with a specific tolerance. Xometry Pro The Meaning Behind "mH"

The designation is split into two distinct parts that cover different aspects of a part's geometry: m (Medium): ISO 2768-1 , which defines general tolerances for linear and angular dimensions . It is the most common class for standard machining. ISO 2768-2 , which covers geometrical tolerances like straightness, flatness, and perpendicularity. The Linear Tolerance Chart (m) For a drawing labeled ISO 2768-m

, the "medium" class allows for specific deviations based on the length of the feature. Larger parts are naturally allowed more "wiggle room" than smaller ones. Protolabs Network Nominal Length Range (mm) Tolerance (± 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 ZEISS Quality Forum The Geometric Tolerance Chart (H)

class ensures the overall "shape" of the part is accurate. For instance, it defines how flat a surface must be or how straight an edge needs to stay. Length Range (mm) Straightness & Flatness (mm) Perpendicularity (mm) 100 to 300 300 to 1000 Scribd - ISO 2768 General Tolerances Guide Why Engineers Love It What is ISO 2768? | CNC Machining Tolerance Standards

The designation ISO 2768-mh defines a standard set of general tolerances for engineering drawings that lack individual tolerance specifications. It is divided into two parts: Part 1 (m): (m) tolerance for linear and angular dimensions. Part 2 (h):

class tolerance for geometric features like straightness, flatness, and perpendicularity. ISO 2768-1: Linear Dimensions (Medium Class "m")

These tolerances apply to external/internal sizes, diameters, and distances. Values are in millimeters ( skolarium.com Nominal Size Range ( Medium (m) Tolerance plus or minus 0.1 plus or minus 0.1 plus or minus 0.2 plus or minus 0.3 plus or minus 0.5 plus or minus 0.8 plus or minus 1.2 plus or minus 2.0 ISO 2768-1: Broken Edges (External Radii & Chamfers) Nominal Size Range ( Medium (m) Tolerance plus or minus 0.2 plus or minus 0.5 plus or minus 1.0 ISO 2768-2: Geometric Tolerances (Class "H")

Geometric tolerances control the shape and orientation of features. The Basics of General Tolerance Standard – ISO 2768-mK

ISO 2768-mh specifies general tolerances for linear and angular dimensions of metal parts produced by machining or metal removal. This standard is designed to simplify drawings by establishing standard tolerances for features that don't require specific, tighter precision. The "mh" designation indicates two separate classes: m: Medium class for linear and angular dimensions.

h: Tolerance class for geometrical tolerances (straightness, flatness, etc.). 1. Linear Dimensions (ISO 2768-m)

The following tolerances apply to linear dimensions such as external sizes, internal sizes, step sizes, diameters, and radii. Nominal Size Range (mm) Tolerance (± 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 2. External Radii and Chamfer Heights

These tolerances apply to broken edges, such as external radii and chamfer heights. Nominal Size Range (mm) Tolerance (± mm) Over 3 to 6 3. Angular Dimensions iso 2768-mh tolerance chart

These tolerances apply to angular dimensions, usually expressed in degrees and minutes. Length of Shorter Leg (mm) Tolerance (±) 1∘1 raised to the composed with power Over 10 to 50 Over 50 to 120 Over 120 to 400 4. Geometrical Tolerances (ISO 2768-h)

The "h" class defines the general tolerances for geometric characteristics. Straightness and Flatness: Up to 10 mm: 0.1 mm 10 to 30 mm: 0.2 mm 30 to 100 mm: 0.4 mm 100 to 300 mm: 0.8 mm 300 to 1000 mm: 1.2 mm

Perpendicularity: Max 0.4 mm (for ranges up to 300 mm) to 0.6 mm (over 300 mm). Symmetry: 0.5 mm. Run-out: 0.1 mm. Usage Summary

When you see ISO 2768-mh on a technical drawing, it means that unless otherwise specified, the workshop must adhere to the Medium linear tolerances and High (h) geometric tolerances listed above. This approach reduces drafting time and clarifies which dimensions are critical versus standard.

The ISO 2768-mH tolerance chart is an essential standard in mechanical engineering used to simplify technical drawings by providing default tolerances for features that do not have individually specified limits. By referencing "ISO 2768-mH," designers ensure that parts remain functional and manufacturable without the clutter of excessive dimensioning. What Does "mH" Mean?

The designation is composed of two parts from the ISO 2768 standard: Standard Tolerances in Manufacturing: ISO 2768 & ISO 286

The ISO 2768-mH callout is a common engineering standard that sets "medium" general tolerances for a part's size and geometry. Instead of labeling every single dimension with a plus-minus value, adding "ISO 2768-mH" to your drawing's title block establishes a global default for all untoleranced features.

m: Stands for Medium precision for linear and angular dimensions (Part 1).

H: Stands for High precision for geometrical tolerances like flatness and perpendicularity (Part 2). ISO 2768-1: Linear & Angular (Class 'm')

These values apply to lengths, diameters, and angles that don't have an individual tolerance. Linear Dimensions (in mm) For lengths, widths, and diameters: Nominal Size Range (mm) Tolerance (± mm) over 3 to 6 over 6 to 30 over 30 to 120 over 120 to 400 over 400 to 1000 External Radii & Chamfer Heights Used for rounded edges or beveled corners: Nominal Size Range (mm) Tolerance (± mm) over 3 to 6 Angular Dimensions Applies to the shorter leg of the angle: Nominal Length Range (mm) Tolerance (±) over 10 to 50 over 50 to 120 ISO 2768-2: Geometrical Tolerances (Class 'H')

The "H" class defines how flat, straight, or square a part must be. Feature Type Basic Range (mm) Tolerance (mm) Flatness & Straightness over 10 to 30 over 30 to 100 Perpendicularity Symmetry Circular Run-out All ranges When to Use ISO 2768-mH

Cost Efficiency: Use these general tolerances for non-critical features to avoid over-engineering and high machining costs.

Simplicity: It keeps technical drawings clean and easy to read.

Note: If a feature is critical for function—like a bearing fit or a sealing surface—you should override this by adding a specific tolerance (e.g., ISO 286) directly to that dimension. General Tolerance - ISO 2768 1 & 2 - ZEISS Quality Forum

ISO 2768-mH is a combination designation used in engineering drawings to specify general tolerances for parts without individual tolerance indications. It combines two distinct parts of the ISO 2768 standard: "m" (medium precision) for linear and angular dimensions, and "H" (high precision) for geometrical features. Understanding the "mH" Designation The existence of this chart does not mean

"m" (Part 1 - Linear & Angular): Stands for the Medium tolerance class under ISO 2768-1. It covers external and internal sizes, radii, and chamfer heights.

"H" (Part 2 - Geometrical): Stands for the highest precision class under ISO 2768-2. It defines limits for straightness, flatness, perpendicularity, and symmetry. ISO 2768-m (Linear Dimensions)

The "m" class provides standard permissible deviations based on the nominal length of the feature. Nominal Length Range (mm) Tolerance (± 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 Values sourced from ISO 2768-1 standards. ISO 2768-H (Geometrical Tolerances)

The "H" class is the most restrictive general geometrical tolerance, typically used for high-precision CNC machining.

Straightness & Flatness: For a length up to 10mm, the tolerance is 0.02mm. For lengths over 1000mm to 3000mm, it is 0.4mm.

Perpendicularity: Deviations range from 0.2mm (up to 100mm length) to 0.5mm (over 1000mm).

Symmetry: Fixed at a maximum of 0.5mm for all ranges in class H. Application and Benefits General Tolerance - ISO 2768 1 & 2 - ZEISS Quality Forum

Recommended title block note examples:

❌ Applying mH to shafts – H is for holes only. For shafts, use “mK” or specify individually.
❌ Assuming bilateral tolerances for holes – H holes are unilateral (+/0).
❌ Using mH for welded or cast parts – ISO 2768 is for metal removal (machining), not raw castings.
❌ Forgetting angular tolerances – 1 degree is large. If you need 0.5°, specify it.

Many engineers misread the chart because they forget the scaling rule for geometric tolerances. Let’s walk through three real-world scenarios.

Do not rely on ISO 2768-mH for:

Would you like this content as a printable PDF-ready table or a markdown file for your documentation?

Understanding ISO 2768-MH Tolerance Chart: A Comprehensive Guide

In the world of engineering and manufacturing, tolerances play a crucial role in ensuring that parts and components fit together seamlessly. One of the most widely used tolerance standards is ISO 2768, which provides a set of general tolerances for linear and angular dimensions. In this blog post, we'll dive into the specifics of the ISO 2768-MH tolerance chart, exploring its significance, application, and interpretation. Recommended title block note examples: ❌ Applying mH

What is ISO 2768?

ISO 2768 is an international standard that defines general tolerances for linear and angular dimensions. The standard provides a set of tolerances that can be applied to various features, such as lengths, widths, heights, and angles. The goal of ISO 2768 is to ensure that parts and components can be manufactured and assembled with a reasonable degree of accuracy, while also allowing for some degree of variation.

Understanding the ISO 2768-MH Tolerance Chart

The ISO 2768-MH tolerance chart is a specific part of the ISO 2768 standard, which defines the tolerances for medium (M) and high (H) accuracy classes. The chart provides a set of tolerance values for different feature types, including:

The ISO 2768-MH tolerance chart consists of several columns, which represent the following:

Interpreting the ISO 2768-MH Tolerance Chart

To interpret the ISO 2768-MH tolerance chart, follow these steps:

For example, suppose we have a linear dimension with a nominal size of 100 mm. We want to apply a tolerance class M. According to the ISO 2768-MH tolerance chart, the tolerance value for a linear dimension with a nominal size between 80 mm and 120 mm is ±0.5 mm.

Significance of ISO 2768-MH Tolerance Chart

The ISO 2768-MH tolerance chart is significant in various industries, including:

Best Practices for Using the ISO 2768-MH Tolerance Chart

To get the most out of the ISO 2768-MH tolerance chart, follow these best practices:

Conclusion

The ISO 2768-MH tolerance chart is a valuable resource for engineers and manufacturers, providing a set of general tolerances for linear and angular dimensions. By understanding and applying the tolerances outlined in this chart, designers and manufacturers can ensure that their parts and components fit together seamlessly, while also minimizing costs and maximizing efficiency. Whether you're working in aerospace, automotive, or medical devices, the ISO 2768-MH tolerance chart is an essential tool to have in your toolkit.

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