Iso 2768-mh Tolerance Chart ((better)) -

The ISO 2768-mh standard is a globally recognized guideline used in mechanical engineering to simplify technical drawings by defining general tolerances for linear and angular dimensions. When a drawing specifies "ISO 2768-mh" in its title block, it establishes a default level of precision for every feature that doesn't have a specific, individual tolerance applied to it. Breaking Down "mH"

The designation is split into two parts, representing different tolerance classes:

m (Medium): Refers to Part 1 of the standard, covering linear and angular dimensions (e.g., lengths, diameters, radii).

H (High): Refers to Part 2 of the standard, covering geometrical tolerances like straightness, flatness, and perpendicularity. ISO 2768-1: Linear Dimensions (Class m)

The "m" (medium) class is the most common standard used in CNC machining. It provides a balanced approach between manufacturing cost and part functionality. Nominal Size Range (mm) Tolerance (± mm) Over 3 to 6 Over 6 to 30 Over 30 to 120 Over 120 to 400 Over 400 to 1000 Over 1000 to 2000 Over 2000 to 4000 Source: ZEISS Quality Forum ISO 2768-2: Geometrical Tolerances (Class H) iso 2768-mh tolerance chart

The "H" class defines the permissible limits for the form and position of features.

Straightness & Flatness: Ranges from 0.02 mm for lengths up to 10 mm, up to 0.5 mm for lengths over 1000 mm.

Perpendicularity: Ranges from 0.2 mm to 0.5 mm depending on the length of the shorter side. Symmetry: Standardized at 0.5 mm for this class. Circular Run-out: Set at 0.1 mm. Why Use ISO 2768-mh? General Tolerance - ISO 2768 1 & 2 - ZEISS Quality Forum

Scenario 3: Thin Wall (0.8mm thickness)

What is ISO 2768? The Foundation

Before diving into the specific "mH" class, we must understand the standard. ISO 2768 is split into two parts: The ISO 2768-mh standard is a globally recognized

  1. ISO 2768-1 (1990): Tolerances for linear and angular dimensions.
  2. ISO 2768-2 (1989): Geometrical tolerances for features (straightness, flatness, perpendicularity, symmetry, runout).

When you see "ISO 2768-mH," you are actually looking at a hybrid notation. The 'm' refers to the "Medium" class for linear dimensions (from Part 1). The 'H' refers to the "H" grade for geometrical tolerances (from Part 2), which is commonly translated as "Medium" for geometrics.

In practice, "ISO 2768-mH" means: All unspecified linear dimensions follow the 'm' (Medium) tolerance band, and all unspecified geometrical tolerances follow the 'H' grade.

ISO 2768-mH Tolerance Chart: The Ultimate Guide for Engineers & Machinists

If you’ve ever looked at a mechanical drawing and seen the note “ISO 2768-mH” in the title block, you’ve likely wondered: What exactly does this allow? How much deviation is acceptable?

You’re not alone.

ISO 2768 is one of the most widely used general tolerance standards for machined and fabricated parts. The “m” stands for medium (the tolerance class), and the “H” refers to the general tolerances for hole dimensions.

In this guide, we’ll break down:

Straightness & Flatness

| Nominal Length Range (mm) | Tolerance (mm) | |--------------------------|----------------| | ≤ 10 | 0.02 | | >10 to 30 | 0.05 | | >30 to 100 | 0.1 | | >100 to 300 | 0.2 | | >300 to 1000 | 0.3 | | >1000 to 3000 | 0.4 |