ISO 2768 – General Tolerances in Engineering

Master precision standards for machining and technical drawing.

The reference to simplify your drawings and guarantee the quality of your mechanical parts. Understand tolerance classes f, m, c, v and verify your dimensions instantly.

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ISO 2768-1 Tolerance Simulator

Enter a nominal dimension to get the corresponding tolerance according to the chosen class.

Valid from 0.5 mm to 4000 mm

Understanding ISO 2768 Standard

In Brief

  • Simplification: A standard that lightens drawings via general tolerances rather than detailed ones everywhere.
  • Structure: Two parts, ISO 2768-1 (linear/angular) and ISO 2768-2 (geometric).
  • Classes: f, m, c, v (1) and H, K, L (2) define precision.
  • Benefit: Better communication, robust quality control, cost reduction.
  • Exceptions: Critical functions always require a specific tolerance.

Origins and Objectives

The ISO 2768 standard was developed to address a recurring problem: on a drawing, not all dimensions can be over-toleranced without cluttering the reading. The objective is to propose standardized general tolerances, applied by default where no specific requirement is indicated.

This logic is crucial in multipolar production. A client in Europe can have the same part produced in Asia, while maintaining a consistent interpretation.

Official ISO 2768 Tables

General tolerances for linear, angular, and geometric dimensions.

ISO 2768 Tolerance Table
🖨️ Download / Print Full Tables (PDF)

The Two Parts of the Standard

  • 📏
    ISO 2768-1 (Designation e.g.: ISO 2768-m)

    Concerns linear tolerances (lengths, diameters, distances) and angular ones. The class (f, m, c, v) defines fineress. A medium class (m) is suitable for most standard parts.

  • 📐
    ISO 2768-2 (Designation e.g.: ISO 2768-K)

    Concerns geometric tolerances: straightness, flatness, perpendicularity, symmetry, run-out. Classes H, K, L. Essential to ensure assembly without specifying everything.

Value Added in Industry

In a world where deadlines compress, tolerance is an economic lever:

  • Too tight: Exploding costs and unnecessary scrap.
  • Too loose: Assembly and reliability problems.
  • ISO 2768 (The Middle Way): Fewer back-and-forths, targeted controls, and reproducible quality.

Application Areas

CNC Machining & General Mech

Serves as a base for chassis, housings, tooling. Avoids cluttering control programs for secondary dimensions.

Aerospace & Automotive

Used for non-critical elements or environment parts, allowing quality effort to focus on safety zones.

⚠️ Mind the Exceptions

ISO 2768 does not replace functional analysis. As soon as a dimension conditions a fit (bearing), a seal, or safety, a specific tolerance must be explicit on the drawing.

Frequently Asked Questions (FAQ)

Where to indicate ISO 2768 on a drawing?

The mention is placed in the title block, with the chosen class (e.g., "ISO 2768-mK"). Thus, general tolerances apply to all dimensions not individually toleranced.

Is ISO 2768 sufficient for critical parts?

No. It serves as a base for standard features. Critical zones (bearings, precise guides) require a specific explicit tolerance.

What is the difference between ISO 2768-1 and -2?

Part 1 handles dimensions (lengths, angles). Part 2 handles form (flatness, perpendicularity, symmetry). Both are complementary.

How to choose a class without extra cost?

Do not choose "fine" (f) by default! A "medium" (m) class is often the right compromise. A class that is too fine imposes unnecessary machining and control costs for non-functional surfaces.

What to do in case of a supplier dispute?

If the standard is cited on the drawing, it is contractual. Check the indicated class and align measurement methods. This is the advantage of an ISO standard: it reduces subjectivity.