"The 'H' means the same as the 'm'." Reality: No. 'H' is specifically from ISO 2768-2. It defines geometry, not size. A part can be the wrong size (within 'm') but perfectly flat (within 'H').
Tolerance (grade m) for length L (mm):
To legally invoke this standard, you must write it in the title block or general notes. The standard syntax is critical.
The 'H' grade corresponds to the "Medium" geometric class. Here is the for geometry: iso 2768-mh tolerance chart
For example, if the nominal angle of a part is 45°, the tolerance value would be ±1.0°.
The answer is cost. Tight tolerances require grinding, lapping, and CMM inspection. If a 100mm long cosmetic cover plate is dimensioned at 100mm ±0.01mm because the drafter forgot to set defaults, the part will cost 500% more than necessary.
For angles without individual tolerances: "The 'H' means the same as the 'm'
For example, a highly precise aerospace part might require , while a rough welded construction frame might only need ISO 2768-cL . If you(CNC machining, injection molding, sheet metal, etc.) What is the material of your part? Are you experiencing any specific fitment issues ? Share public link
The "h" class defines the general tolerances for geometric characteristics. : Up to 10 mm: 0.1 mm 10 to 30 mm: 0.2 mm 30 to 100 mm: 0.4 mm 100 to 300 mm: 0.8 mm 300 to 1000 mm: 1.2 mm
Class H is the highest precision geometric tolerance class. Values apply to features (flatness, straightness, perpendicularity, symmetry, circular runout) unless a tighter tolerance is specified. A part can be the wrong size (within
The is an invaluable tool in modern engineering. It bridges the gap between design intent and manufacturing practicality. By placing a simple note on a drawing title block, engineers can communicate explicit expectations for both dimension sizes and geometric forms.
for geometrical tolerances (often mistakenly written as 'h', but corresponds to H in the standard).
In practice, for most machined parts under 120 mm, you get ±1 degree.