Iso 2768-mh Tolerance Chart -
Stands for the highest precision class under ISO 2768-2 . It defines limits for straightness, flatness, perpendicularity, and symmetry. ISO 2768-m (Linear Dimensions)
❌ – 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. iso 2768-mh tolerance chart
: On a technical drawing, you would write: ISO 2768-mH (or commonly ISO 2768-mh ) Stands for the highest precision class under ISO 2768-2
The designation indicates a specific combination of general tolerances for a technical drawing. The first lowercase letter ( m ) refers to "medium" tolerances for linear and angular dimensions (Part 1), while the second uppercase letter ( H ) refers to the highest precision class for geometrical features (Part 2). Understanding ISO 2768-mh For shafts, use “mK” or specify individually
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.
