For nominal sizes like lengths, widths, external diameters, and step heights, the allowable deviations are based on the dimension range: Nominal Size Range (mm) Tolerance Limit for Class m (mm) ±0.1plus or minus 0.1 ±0.1plus or minus 0.1 ±0.2plus or minus 0.2 ±0.3plus or minus 0.3 ±0.5plus or minus 0.5 ±0.8plus or minus 0.8 ±1.2plus or minus 1.2 ±2.0plus or minus 2.0 Broken Edges Tolerance Chart (Class m) For external radii and chamfer heights: Nominal Size Range (mm) Tolerance Limit for Class m (mm) ±0.2plus or minus 0.2 ±0.5plus or minus 0.5 ±1.0plus or minus 1.0 Angular Dimensions Tolerance Chart (Class m)
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.
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.
: The general tolerance for symmetry under Class H is 0.5 mm . iso 2768-mh tolerance chart
The following tables show the permissible deviations for dimensions when "ISO 2768-mH" is referenced on a drawing. Table A: Linear Dimensions (ISO 2768-1 Medium - 'm')
: H (Tight), K (Medium), L (Loose).
In precision engineering and manufacturing, clear communication between designers and machinists is vital. The is an international standard used to simplify technical drawings by defining general tolerances for linear and angular dimensions (class m) and geometrical tolerances (class h) [1, 2]. For nominal sizes like lengths, widths, external diameters,
'f' is too expensive for base material. 'c' is too loose for mating holes. 'mH' balances cost and functionality for 80% of mechanical parts.
To implement this standard legally and contractually on a technical blueprint, add the designation directly to or near the title block. "General tolerances according to ISO 2768-mh"
Class "m" linear tolerances align perfectly with standard CNC milling, routing, and turning capabilities. Machinists can run parts quickly without slowing down to maintain unnecessarily tight tolerances. : The general tolerance for symmetry under Class H is 0
"If I write ISO 2768-mh, I never have to tolerance diameters." Reality: Diameters (like a Ø10mm hole) follow the SAME linear chart. A Ø10mm hole could be Ø10.2mm. That is an H11 tolerance loose fit. For a running fit, you still need an explicit H7 or G6.
Are there any that require tighter tolerances? Share public link