| Îøèáêà |
If a feature matters for function or fit, give it an explicit tolerance. ISO 2768-MK-E is for everything else.
For production shops, understanding this shorthand reduces errors and clarifies expectations. For designers, using it correctly (and knowing its limits) produces clear, manufacturable drawings without over-tolerancing. iso 2768-mk-e
These values apply per 100 mm of length. For longer lengths, the tolerance is prorated but limited by the maximum deviation. If a feature matters for function or fit,
| Feature Type | Rule | |--------------|------| | Length, width, height | ± mm from "M" linear table | | Hole diameter | Not covered (size tolerance must be given individually unless it's a general dimension) | | Hole position | Covered by "K" position tolerance (0.5 mm per 100 mm) | | Flatness of a surface | 0.2 mm per 100 mm (class K) | | Perpendicularity of a shoulder | 0.5 mm per 100 mm (class K) | | External fillet radius R5 | ±1.0 mm (since 5 mm is in >3–6 range, "E") | | Chamfer C2 | ±0.5 mm (from "E" table) | For designers, using it correctly (and knowing its
| Part | Title | Purpose | |------|-------|---------| | | General tolerances for linear and angular dimensions | Defines tolerance classes (f, m, c, v) for sizes, radii, chamfers, and angles | | ISO 2768-2 | General tolerances for geometrical features | Defines tolerance classes (H, K, L) for straightness, flatness, parallelism, perpendicularity, symmetry, runout |
– Same values as perpendicularity. Circular runout – 0.2 mm (class K). Total runout – Not defined; must be specified individually. Example: A 200 mm long machined surface without a flatness callout → allowed flatness deviation = 0.3 mm. 3.3 "E" – External Radii & Chamfer Heights (ISO 2768-1 Annex A) The "E" instructs that tolerances for external radii and chamfer heights follow the same "M" class limits as linear dimensions, but applied to the radius or chamfer size.