This report defines the general tolerance requirements for linear and angular dimensions (Part 1) as well as geometrical features (Part 2) according to . It serves as the default specification for drawings where no individual tolerances are indicated, ensuring uniformity in manufacturing and inspection.
Choosing the right class is a balancing act. While an "m" classification often provides a safe, cost-effective default, critical features still demand their own specific tolerances. By mastering the rules and tables outlined in this guide, you can harness the full potential of the ISO 2768 standard to streamline your designs, control manufacturing costs, and ensure consistent quality on every part you produce.
Choosing the correct tolerance class is a critical design decision that directly impacts manufacturing cost and feasibility.
Under ISO 2768-1, there are four tolerance classes: fine (f), medium (m), coarse (c), and very coarse (v). The , which is the industry standard for conventional CNC machining, milling, and turning. general tolerance iso 2768-mk
Simplified angular tolerance:
For nominal sizes below 0.5 mm, the deviation shall be indicated directly adjacent to the relevant nominal size.
Instead of thousands of individual ± signs, you have one note in the title block. This report defines the general tolerance requirements for
The "m" designation means the drawing adheres to the tolerance class for basic dimensions. 2. Part 2: Geometrical Tolerances (The uppercase "K")
The designation indicates that a drawing follows medium accuracy limits for linear dimensions (class m) and medium geometric constraints (class K). It serves as a vital bridge between engineering intent and cost-efficient manufacturing.
Permissible Deviations for Broken Edges (External Radii and Chamfers) While an "m" classification often provides a safe,
QE-2024-ISO2768 Date: [Current Date] Prepared by: Engineering Department Subject: Compliance and inspection criteria for machined and fabricated parts using ISO 2768-mk.
Section B (using table) 6. Ø10 mm: a) m: ±0.15 → range 9.85–10.15 mm b) k: ±0.5 → range 9.5–10.5 mm 7. Length 45 mm: a) m: for 30–120 → ±0.2 → 44.8–45.2 mm b) k: for 30–120 → ±0.8 → 44.2–45.8 mm 8. Ø2.5 mm: a) m (≤3) ±0.1 → 2.4–2.6 mm b) k (≤3) ±0.3 → 2.2–2.8 mm 9. Angle 60°: m: ±1.0° → 59.0°–61.0° k: ±3.0° → 57.0°–63.0° If groove requires ±0.05 mm explicit tolerance, that explicit tolerance overrides ISO 2768 for that feature and ISO 2768 does not apply to that groove.
Among its various classifications, is the most widely specified standard in precision machining, sheet metal fabrication, and general engineering. Here is a comprehensive breakdown of what ISO 2768-mK means, its specific tolerance limits, and how to apply it effectively. Decoding "ISO 2768-mK"