Iso 2768-mh Tolerance Chart High Quality May 2026

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

Understanding the 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 the ISO 2768-MH tolerance chart, which provides a set of guidelines for determining the acceptable limits of variation in the dimensions of parts and components. In this article, we will delve into the details of the ISO 2768-MH tolerance chart, its significance, and how to use it effectively.

What is the ISO 2768-MH Tolerance Chart?

The ISO 2768-MH tolerance chart is a part of the ISO 2768 standard, which was first published in 1989 by the International Organization for Standardization (ISO). The standard provides general tolerances for linear and angular dimensions, and it is widely used in various industries, including engineering, manufacturing, and construction.

The "MH" in ISO 2768-MH refers to the specific tolerance class, which is defined as "medium" tolerance. This class provides a balance between the precision required for a part or component and the practical limitations of manufacturing processes.

Significance of the ISO 2768-MH Tolerance Chart

The ISO 2768-MH tolerance chart is significant because it provides a standardized framework for specifying tolerances in engineering drawings and technical documentation. By using this chart, designers, engineers, and manufacturers can ensure that parts and components are interchangeable, and that they meet the required specifications.

The use of the ISO 2768-MH tolerance chart offers several benefits, including:

  1. Interchangeability: Parts and components manufactured to ISO 2768-MH tolerances can be easily interchanged, reducing the need for custom-made parts and minimizing inventory costs.
  2. Reduced manufacturing costs: By specifying tolerances that are achievable with standard manufacturing processes, designers and engineers can reduce the costs associated with producing parts and components.
  3. Improved quality: The ISO 2768-MH tolerance chart helps to ensure that parts and components meet the required specifications, reducing the risk of defects and improving overall quality.

How to Use the ISO 2768-MH Tolerance Chart

The ISO 2768-MH tolerance chart provides a set of tables that list the tolerance values for different types of dimensions, including linear dimensions, angular dimensions, and geometric tolerances.

To use the chart, follow these steps:

  1. Determine the nominal dimension: Identify the nominal dimension of the part or component, which is the theoretical or ideal value of the dimension.
  2. Select the tolerance class: Choose the tolerance class that corresponds to the required level of precision. In this case, we are using the "MH" or medium tolerance class.
  3. Look up the tolerance value: Refer to the relevant table in the ISO 2768-MH tolerance chart and look up the tolerance value that corresponds to the nominal dimension and tolerance class.

ISO 2768-MH Tolerance Chart: Linear Dimensions

The following table provides an excerpt from the ISO 2768-MH tolerance chart for linear dimensions:

| Nominal dimension (mm) | Tolerance value (mm) | | --- | --- | | 6 to 30 | ±0.2 | | 30 to 120 | ±0.3 | | 120 to 400 | ±0.5 | | 400 to 1000 | ±0.8 |

For example, if the nominal dimension of a part is 50 mm, the tolerance value would be ±0.3 mm.

ISO 2768-MH Tolerance Chart: Angular Dimensions iso 2768-mh tolerance chart

The following table provides an excerpt from the ISO 2768-MH tolerance chart for angular dimensions:

| Nominal dimension (°) | Tolerance value (°) | | --- | --- | | 1 to 10 | ±0.5 | | 10 to 50 | ±1.0 | | 50 to 120 | ±2.0 |

For example, if the nominal angle of a part is 45°, the tolerance value would be ±1.0°.

Geometric Tolerances

The ISO 2768-MH tolerance chart also provides guidelines for geometric tolerances, including:

These tolerances are specified in terms of a tolerance zone, which is a defined area or volume within which the feature must lie.

Conclusion

The ISO 2768-MH tolerance chart is a widely used standard that provides a set of guidelines for determining the acceptable limits of variation in the dimensions of parts and components. By understanding how to use this chart, designers, engineers, and manufacturers can ensure that parts and components meet the required specifications, are interchangeable, and are manufactured to a high level of quality.

Whether you are working in the engineering, manufacturing, or construction industry, the ISO 2768-MH tolerance chart is an essential tool to have in your toolkit. By following the guidelines outlined in this article, you can ensure that your parts and components meet the required tolerances, reducing the risk of defects and improving overall quality.

Additional Resources

For more information on the ISO 2768-MH tolerance chart, you can refer to the following resources:

By understanding the ISO 2768-MH tolerance chart and its applications, you can take your designs and manufacturing processes to the next level, ensuring that your parts and components meet the required specifications and are of the highest quality.

Part 1: Linear Dimensions (Class 'm' - Medium)

These tolerances apply to dimensions like lengths, diameters, step heights, and radii.

| Nominal Dimension Range (mm) | Permissible Deviation for Class 'm' (mm) | | :--- | :--- | | 0.5 up to 3 | ± 0.1 | | >3 up to 6 | ± 0.1 | | >6 up to 30 | ± 0.2 | | >30 up to 120 | ± 0.3 | | >120 up to 400 | ± 0.5 | | >400 up to 1000 | ± 0.8 | | >1000 up to 2000 | ± 1.2 | | >2000 up to 4000 | ± 2.0 |

Interpretation: For a shaft with a nominal diameter of 25 mm, the 'm' tolerance allows the actual diameter to be anywhere between 24.8 mm and 25.2 mm. For a longer part of 300 mm, the allowed range is ±0.5 mm (299.5 mm to 300.5 mm).

Introduction: Decoding the Alphabet Soup of Engineering Standards

In the world of mechanical engineering and manufacturing, a drawing is a legal contract between the designer and the machinist. But what happens when a dimension on that drawing has no explicit tolerance value listed next to it?

This is where ISO 2768 comes into play. It is the international savior that defines "general tolerances" for linear and angular dimensions without individual tolerance indications. The ISO 2768-mH tolerance chart is an essential

Among the four tolerance classes (f – fine, m – medium, c – coarse, v – very coarse), one stands out as the undisputed king of job shops, prototype development, and general machinery: ISO 2768-mH.

This article provides an exhaustive breakdown of the ISO 2768-mh tolerance chart, explaining how to read it, apply it, and avoid costly manufacturing mistakes.

Title: Decoding Precision: A Comprehensive Examination of the ISO 2768-mh Tolerance Chart

Conclusion: Mastering the ISO 2768-mh Tolerance Chart

The ISO 2768-mh tolerance chart is the silent workhorse of modern mechanical drawings. By adopting "m" for linear and "H" for geometric tolerances, you strike an optimal balance between manufacturing cost and functional reliability.

Remember the golden rule: Use ISO 2768-mh for non-critical features. Reserve explicit tolerances for fits, functions, and failures. Keep a laminated copy of the chart near your CMM and another in your CAD template. When a machinist asks, "What tolerance goes here?", you can confidently reply: "Check the title block—ISO 2768-mH applies."

Next steps for your engineering workflow:

  1. Audit your current CAD title block. Does it reference ISO 2768?
  2. Train your junior drafters on the difference between Linear (Part 1) and Geometric (Part 2).
  3. For parts smaller than 6mm, consider switching to ISO 2768-f (Fine) to maintain relative precision.

By mastering this standard, you stop over-tolerancing the trivial and start focusing on the true functional interfaces that define great product design.

ISO 2768-mH standard defines general tolerances for parts where specific tolerances aren't individually marked on a drawing. The designation refers to medium dimensional tolerances (Part 1), while refers to high-precision geometrical tolerances (Part 2). Part 1: Dimensional Tolerances (m - Medium)

These apply to linear dimensions like external sizes, internal sizes, and step heights. Nominal Size Range (mm) Tolerance (± mm) > 30 to 120 > 120 to 400 > 400 to 1000 > 1000 to 2000 > 2000 to 4000 Data sourced from Dau Components Part 2: Geometrical Tolerances (H - Fine)

class is the strictest of the three geometrical classes (H, K, L) and governs the form and position of the part. DAU Components 1. Straightness and Flatness Nominal Length (mm) Tolerance (mm) > 10 to 30 > 30 to 100 > 100 to 300 > 300 to 1000 > 1000 to 3000 2. Perpendicularity Nominal Length (mm) Tolerance (mm) > 100 to 300 > 300 to 1000 > 1000 to 3000 3. Symmetry and Run-out : For the H class, the tolerance is for all ranges up to 3000 mm. Circular Run-out : The H class limit is Usage Notes What is ISO 2768? | CNC Machining Tolerance Standards

Fictiv's CNC machining service adheres to the ISO 2768 tolerances, specifically meeting the medium requirements for precision. ISO 2768 General Tolerances Guide | PDF - Scribd

General tolerances on circular run-out Unit : mm Tolerance class H K L Circular run-out tolerance 0.1 0.2 0.5. General Tolerances to DIN ISO 2768 - DAU Components

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

"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. How to Use the ISO 2768-MH Tolerance Chart

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

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

2. The "H" (Geometrical Tolerances)

The 'H' is where things get interesting—and often misunderstood. It stands for Coarse accuracy regarding geometry (straightness, flatness, perpendicularity, symmetry).

Many engineers mistake "Coarse" for "low quality," but in ISO 2768, Class H is the default for typical welded fabrications or general machine parts where strict GD&T is not required.

The Chart at a Glance (ISO 2768-H):

| Nominal Dimension (mm) | Flatness & Straightness | Perpendicularity | Symmetry | | :--- | :--- | :--- | :--- | | Up to 10 | 0.2 | 0.4 | 0.6 | | Over 10 up to 30 | 0.3 | 0.6 | 1.0 | | Over 30 up to 100 | 0.4 | 0.8 | 1.5 | | Over 100 up to 300 | 0.6 | 1.0 | 2.0 |

(Values are in millimeters)

ISO 2768-mH Tolerance Chart: The Ultimate Guide for Engineers & Machinists

If you’ve ever looked at a mechanical drawing and seen the note “ISO 2768-mH” in the title block, you’ve likely wondered: What exactly does this allow? How much deviation is acceptable?

You’re not alone.

ISO 2768 is one of the most widely used general tolerance standards for machined and fabricated parts. The “m” stands for medium (the tolerance class), and the “H” refers to the general tolerances for hole dimensions.

In this guide, we’ll break down: