O-ring grooves and sealing surfaces require incredibly strict depth controls and superior surface finishes to prevent leaks.

If a feature is critical for a "press-fit" (like a bearing housing) or requires extreme precision for airtight seals, . In those specific cases, you must manually define a tighter tolerance (e.g., +/- 0.01mm) directly on that dimension.

Class specifies the allowable deviation for the shape and position of features. Feature Type Range (mm) Tolerance (mm) Straightness & Flatness 100 to 300 Perpendicularity 100 to 300 Symmetry Circular Run-out All ranges Sources: Why Use ISO 2768-mH?

The Ultimate Guide to the ISO 2768-mh Tolerance Chart in Manufacturing

: Class "m" offers a realistic balance. It is tight enough for functional assembly but loose enough to prevent expensive, over-engineered machining processes.

The designation "ISO 2768-mh" combines a specific precision level from Part 1 and Part 2. The Meaning of "m" (Medium)

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

: Designers spend less time calculating non-critical tolerances.

Each grade is applied to ranges of nominal sizes. The tolerance for a dimension equals the tolerance value from the chart corresponding to the nominal size and selected grade. The “m” grade gives moderate tolerances suitable for general machining.

: Governs geometrical tolerances like flatness and symmetry (Classes: H, K, L). Breaking Down "ISO 2768-mh"

This table defines the permitted deviation for angles, based on the length of the shorter side. The tolerances for the medium (m) class are identical to the fine (f) class.

Using this specific standard class provides several distinct operational advantages:

The parallelism tolerance is equal to the numerical value of the straightness/flatness tolerance, or the perpendicularity tolerance—whichever is . Symmetry and Circular Run-Out (Class H)