ISO 2768‑m is a pragmatic choice for default tolerances in many mechanical drawings, balancing manufacturability and reasonable accuracy. It should be used judiciously: clearly noted on drawings, combined with explicit tolerances or GD&T for function-critical features, and aligned with manufacturing and inspection capabilities.

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

All values in mm.

When you see on a drawing, it dictates the precision level for both linear dimensions and geometrical features. This article provides a deep dive into the ISO 2768-mh tolerance chart , explaining what "m" and "h" mean, how to read the charts, and how to apply them correctly. What is ISO 2768?

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 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.

callouts, you simply put "ISO 2768-mh" in your drawing's notes block [1, 3]. Machinists instantly know how to handle non-critical dimensions [1]. 2. Reduced Manufacturing Costs

The ISO 2768-mh tolerance chart is a masterclass in engineering standardization—a compact, intelligent, and widely accepted tool that balances the competing demands of precision, cost, and clarity. By mandating a 'medium' flexibility on linear sizes and a 'fine' discipline on geometric form, it provides a sensible default for countless general machining applications, from mounting brackets to simple enclosures. However, its very convenience is its greatest risk. The chart is a starting point, not a finish line. The responsible engineer must recognize when to override the default, applying specific calculated tolerances for critical fits, evaluating the compatibility of the 'm' and 'h' classes with the chosen manufacturing process, and always, always considering the real-world function of the part. Mastery of ISO 2768-mh lies not in memorizing its numbers, but in understanding the profound engineering judgment that dictates when to apply it, and when to draw a red circle and specify a tighter, functional tolerance. In that judgment, the chart transcends its role as a table of numbers and becomes a true design philosophy.

If a part fails to fit because an unlabeled dimension was cut too loosely, the ISO 2768-mh standard acts as a legal and technical contract. If the machinist stayed within the "m" and "h" ranges, the error lies in the design; if they exceeded it, the part is defective. When Should You NOT Use ISO 2768-mh?

| Nominal Length Range in mm of the shorter side of the angle (approx.) | Tolerance Class "m" | | :--- | :--- | | up to 10 | ±1° | | over 10 up to 50 | ±0°30' | | over 50 up to 120 | ±0°20' | | over 120 up to 400 | ±0°10' | | over 400 | ±0°5' |

This sub-category covers external radii and chamfer heights for broken edges. Nominal Size Range (mm) Tolerance Limit (mm) Over 3 to 6 Angular Dimensions Tolerance Table (Class m)