1. Introduction ISO 2768-MK-E is a combined shorthand notation used on engineering drawings and technical documents. It references three parts of the ISO 2768 standard, which specifies default tolerances for linear dimensions, angular dimensions, geometrical features (form, orientation, location, and runout), and the indication of "E" for general external radius and chamfer dimensions.
GENERAL TOLERANCES: ISO 2768-MK-E Alternatively:
| 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 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.
These values apply per 100 mm of length. For longer lengths, the tolerance is prorated but limited by the maximum deviation.