Iso 2768-mh Tolerance Chart ((better)) 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

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.

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

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

The Structure of ISO 2768: General Tolerances

To understand the "mh" combination, one must first understand the parent standard, ISO 2768. It is divided into two parts:

ISO 2768-1 (1990): Covers tolerances for linear and angular dimensions without individual tolerance indications. It defines four tolerance classes: f (fine) , m (medium) , c (coarse) , and v (very coarse) .
ISO 2768-2 (1989): Covers geometrical tolerances (form: straightness, flatness, circularity, cylindricity; and orientation: parallelism, perpendicularity, symmetry, runout) for features without individual indications. It defines three tolerance classes: H (fine) , K (medium) , and L (coarse) .

Thus, the notation "ISO 2768-mh" instructs the manufacturer to apply the 'm' (medium) class from Part 1 for linear/angular dimensions, and the 'h' (fine) class from Part 2 for geometrical tolerances.

2. Scope and applicability

ISO 2768‑1 applies to linear and angular dimensions on drawings for products manufactured by conventional methods (machining, forming, casting, forging) when tighter tolerances are not specified. ISO 2768‑2 addresses geometrical tolerances (flatness, perpendicularity, etc.) and complements the first part. Use ISO 2768 when:

You want to avoid placing individual tolerances on every dimension.
The functional requirements tolerate the default deviations given.
Parts are produced by common manufacturing processes where extreme precision is unnecessary.

Do not use ISO 2768 when:

Functional fits, assemblies, or interchangeability require specific tolerances.
High-precision components (e.g., bearings, hydraulic components) need tighter control.
Surface finish, material behavior, or thermal effects demand bespoke tolerance schemes.

Important Notes

Drawing notation: On a technical drawing, you would write:
ISO 2768-mH (or commonly ISO 2768-mh)
Not applicable for:
- Dimensions affecting functional fit
- Threaded features
- Press fits
- Dimensions already toleranced individually
Broken edges: Unless specified, external broken edges (chamfers/radii) follow linear tolerance class m: ±0.1 to ±2.0 depending on size.

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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. iso 2768-mh tolerance chart

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:

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.
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.
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:

Determine the nominal dimension: Identify the nominal dimension of the part or component, which is the theoretical or ideal value of the dimension.
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.
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

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:

Straightness
Flatness
Roundness
Cylindricity
Perpendicularity

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:

ISO 2768-1:1989: "General tolerances -- Part 1: Linear and angular dimensions"
ISO 2768-2:1989: "General tolerances -- Part 2: Geometric tolerances"
ANSI/ASME Y14.5-2009: "Dimensioning and Tolerancing"

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.

For engineers, machinists, and designers, defining every single dimension on a technical drawing with a specific tolerance is both time-consuming and prone to error. This is where ISO 2768-mh comes in.

This international standard simplifies technical drawings by providing "general tolerances." If a specific tolerance isn't noted next to a dimension, the workshop refers to this chart to understand the allowable margin of error.

Below is a comprehensive breakdown and the actual charts for the "m" (medium) and "h" (high/fine) classes. Understanding the ISO 2768-mh Designation The code is split into two parts:

ISO 2768-1 (m): This defines the tolerances for linear and angular dimensions (length, radii, diameters). The "m" stands for Medium. The ISO 2768-mH tolerance chart is an essential

ISO 2768-2 (h): This defines the tolerances for geometrical characteristics (flatness, straightness, symmetry). The "h" stands for High (the strictest level for geometry). Part 1: ISO 2768-1 (Linear Dimensions)

These tolerances apply to all linear dimensions like external sizes, internal sizes, steps, diameters, and thread pitches. Table 1: Linear Dimensions (Tolerance Class m) Values in millimeters (mm) Range (mm) 120 to 400 400 to 1000 1000 to 2000 Class m (Medium) Table 2: External Radii and Chamfer Heights Range (mm) 6 and over Class m (Medium) Table 3: Angular Dimensions Length of Short Side (mm) 120 to 400 Class m (Medium) Part 2: ISO 2768-2 (Geometrical Tolerances)

The "h" designation refers to the geometric accuracy of the part. This ensures the part isn't just the right size, but also the right shape. Table 4: Straightness and Flatness (Class h) Range (mm) 100 to 300 300 to 1000 1000 to 3000 Class h (High) Table 5: Perpendicularity (Class h) Range (mm) 100 to 300 300 to 1000 1000 to 3000 Class h (High) Table 6: Symmetry and Circular Run-out Symmetry (Class h): 0.5 mm maximum. Circular Run-out (Class h): 0.1 mm maximum. Why Use ISO 2768-mh?

Cleaner Drawings: You don't have to clutter your CAD exports with "±" values for every single fillet or shoulder.

Cost Efficiency: Using "Medium" tolerances for non-critical areas prevents the machine shop from over-engineering the part, which saves you money.

Global Standardization: Whether your part is being machined in Germany, the US, or China, "ISO 2768-mh" means exactly the same thing. How to Indicate it on Your Drawing

To implement this, simply add a note in or near the title block of your technical drawing: General Tolerances: ISO 2768-mh When NOT to Use It

If a feature is critical for a "press-fit" (like a bearing housing) or requires extreme precision for airtight seals, do not rely on ISO 2768. In those specific cases, you must manually define a tighter tolerance (e.g., +/- 0.01mm) directly on that dimension.

The ISO 2768-mh standard is a specific designation within the international manufacturing framework used to simplify technical drawings by providing general tolerances for parts produced by machining or metal removal .

When a drawing specifies "ISO 2768-mh," it refers to two distinct parts of the standard:

m (Part 1): Medium tolerance class for linear and angular dimensions .

h (Part 2): High tolerance class for geometrical characteristics (form and orientation) . ISO 2768-1: Linear Dimensions (Class m)

The "m" (medium) class is the most common standard for general CNC machining . It provides acceptable variance for lengths, radii, and diameters based on the nominal size of the feature . Nominal Size Range (mm) Tolerance (± mm) for Class m Over 3 to 6 Over 6 to 30 Over 30 to 120 Over 120 to 400 Over 400 to 1000 Over 1000 to 2000 ISO 2768-2: Geometrical Tolerances (Class h)

The "h" class defines the permissible deviations for the shape and orientation of a part, such as how flat a surface must be or how perpendicular two edges are .

Straightness and Flatness: For a length up to 10mm, class h allows a tolerance of 0.02mm. For lengths over 1000mm, it allows up to 0.5mm .

Perpendicularity: Based on the length of the shorter side. For sides up to 100mm, class h allows 0.2mm variance .

Symmetry: Limits the deviation of two features from a common center line. For lengths up to 100mm, the tolerance is 0.5mm . Why Use ISO 2768-mh?

Simplified Drawings: Instead of labeling every single dimension with a tolerance, designers can simply reference "ISO 2768-mh" in the title block .

Cost Efficiency: Using general tolerances ensures that parts aren't over-engineered with unnecessarily tight (and expensive) limits where they aren't needed .

Consistency: It provides a universal language for manufacturers and clients globally, reducing the risk of misinterpretation .

For more complex parts, you can explore the ISO 2768-1 Full Documentation or technical guides from manufacturers like Fictiv and 3ERP for detailed application in CNC machining.

Are you looking to apply these tolerances to a specific material like aluminum or plastic, which might require different considerations? General Tolerance - ISO 2768 1 & 2 - ZEISS Quality Forum

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.

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 ISO 2768-1 (1990): Covers tolerances for linear and

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:

Linear dimensions (e.g., lengths, widths, heights)
Angular dimensions (e.g., angles, tapers)
Geometric tolerances (e.g., flatness, straightness, circularity)

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

Tolerance class: Indicates the accuracy class, which can be Medium (M) or High (H).
Nominal dimension: The nominal size of the feature being toleranced.
Tolerance value: The allowed variation from the nominal dimension.

Interpreting the ISO 2768-MH Tolerance Chart

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

Identify the feature type (e.g., linear dimension, angular dimension).
Determine the nominal dimension of the feature.
Choose the desired tolerance class (M or H).
Look up the tolerance value in the chart.

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:

Aerospace: Where precise tolerances are critical to ensure the safe and efficient operation of aircraft and spacecraft.
Automotive: Where tolerances play a crucial role in ensuring the proper fit and function of vehicle components.
Medical devices: Where tight tolerances are essential to ensure the safety and efficacy of medical implants and instruments.

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:

Understand the application: Consider the specific requirements of your design and the manufacturing process.
Choose the right tolerance class: Select the tolerance class that balances accuracy and cost.
Verify with GD&T: Use Geometric Dimensioning and Tolerancing (GD&T) to provide more detailed and specific tolerances.

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.

References

ISO 2768-1:1989, General tolerances - Part 1: Tolerances for linear and angular dimensions without individual tolerance indications
ISO 2768-2:1989, General tolerances - Part 2: Tolerances for geometric tolerances without individual tolerance indications

Downloadable Resources

ISO 2768-MH Tolerance Chart (PDF)
GD&T Symbols and Terms (PDF)

Related Posts

Understanding Geometric Dimensioning and Tolerancing (GD&T)
The Importance of Tolerance Analysis in Engineering Design
A Guide to ASME Y14.5-2009 Dimensioning and Tolerancing Standards

7. Application rules and drawing practice

Indicate on the drawing that unspecified linear and angular tolerances conform to ISO 2768‑m; commonly done in the title block as “Tolerances: ISO 2768‑m”.
When critical, still specify individual tolerances or use GD&T. ISO 2768 is for non-critical dimensions only.
Avoid mixing tolerance philosophies — if you apply ISO 2768, ensure all stakeholders know which standard edition is referenced.
Dimensions in different units: ISO 2768 tables assume millimetres; for other units, convert appropriately or use equivalent local rules.

Recommended title block note examples:

“Tolerances unless otherwise specified: ISO 2768‑m (linear/angular).”
Or more explicitly: “General tolerances to ISO 2768‑1 grade m; geometric tolerances to ISO 2768‑2 grade m where not specified.”

What Is ISO 2768?

ISO 2768 is an international standard titled “General tolerances for linear and angular dimensions without individual tolerance indications.”

In plain English: If a dimension on your drawing has no specific tolerance next to it, ISO 2768 tells the machinist what’s allowed.

The standard has two parts:

ISO 2768-1 – Linear and angular dimensions
ISO 2768-2 – Geometrical tolerances (flatness, straightness, etc.)

The “mH” designation pulls from both parts.

How to Specify ISO 2768-mh on a Drawing

To legally invoke this standard, you must write it in the title block or general notes. The standard syntax is critical.

Correct notation:

ISO 2768-mH

Alternatively (for clarity):

General tolerances according to ISO 2768-1 (Class m) and ISO 2768-2 (Class H).

What to avoid: Do not write just "Tolerances: mH" without referencing ISO 2768. The standard implies specific rules for radii, chamfers, and how to treat zero values.

Common Mistakes to Avoid

❌ 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.