The following chart shows the permissible deviations in millimeters (mm) for nominal linear dimensions, commonly used in "m" (Medium) class scenarios. Range of Nominal Lengths (mm) Permissible Deviations (m - Medium) ±0.1plus or minus 0.1 Over 3 to 6 ±0.1plus or minus 0.1 Over 6 to 30 ±0.2plus or minus 0.2 Over 30 to 120 ±0.3plus or minus 0.3 Over 120 to 400 ±0.5plus or minus 0.5 Over 400 to 1000 ±0.8plus or minus 0.8 Over 1000 to 2000 ±1.2plus or minus 1.2 Over 2000 to 4000 ±2.0plus or minus 2.0 Data from standard.
The longer of the two features defines the reference element .
(e.g., aluminum, steel, plastics) you plan to use?
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 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) iso 2768-mh tolerance chart
: Stands for Medium tolerance class for linear and angular dimensions (from ISO 2768-1).
These values apply to lengths, diameters, and angles that don't have an individual tolerance. 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 standard has two parts:
In practice, for most machined parts under 120 mm, you get ±1 degree.
The stands for Medium accuracy. This is the most common standard for general machining. It applies to linear dimensions (lengths, widths, heights) unless a specific tolerance is called out directly on the dimension.
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) The following chart shows the permissible deviations in
Need looser? Use (coarse) for fabrication or weldments.
To get the most out of the ISO 2768-MH tolerance chart, follow these best practices:
These high-precision limits define the allowed deviation for the form and orientation of a part. Feature Range (mm) Tolerance (mm) Perpendicularity Symmetry Run-out All ranges Key Application Rules Nominal Size Range (mm) Tolerance (± mm) for
The primary purpose of this system is to avoid cluttering drawings with tolerance specifications for every single dimension. The general tolerances apply to all dimensions and features that lack an individual tolerance, ensuring cost-effective production. It is crucial to remember that any dimension with a specific tolerance overrides the general tolerance. Always verify that your chosen general tolerances are compatible with your manufacturing processes. Selecting unnecessarily tight tolerances can significantly increase production costs and lead time.