Iso 2768-mh Tolerance Chart

For engineers, machinists, and designers, defining every single dimension on a technical drawing with a specific tolerance is both time-consuming and prone to error. This is where ISO 2768-mh comes in.

This international standard simplifies technical drawings by providing "general tolerances." If a specific tolerance isn't noted next to a dimension, the workshop refers to this chart to understand the allowable margin of error.

Below is a comprehensive breakdown and the actual charts for the "m" (medium) and "h" (high/fine) classes. Understanding the ISO 2768-mh Designation The code is split into two parts:

ISO 2768-1 (m): This defines the tolerances for linear and angular dimensions (length, radii, diameters). The "m" stands for Medium.

ISO 2768-2 (h): This defines the tolerances for geometrical characteristics (flatness, straightness, symmetry). The "h" stands for High (the strictest level for geometry). Part 1: ISO 2768-1 (Linear Dimensions) iso 2768-mh tolerance chart

These tolerances apply to all linear dimensions like external sizes, internal sizes, steps, diameters, and thread pitches. Table 1: Linear Dimensions (Tolerance Class m) Values in millimeters (mm) Range (mm) 120 to 400 400 to 1000 1000 to 2000 Class m (Medium) Table 2: External Radii and Chamfer Heights Range (mm) 6 and over Class m (Medium) Table 3: Angular Dimensions Length of Short Side (mm) 120 to 400 Class m (Medium) Part 2: ISO 2768-2 (Geometrical Tolerances)

The "h" designation refers to the geometric accuracy of the part. This ensures the part isn't just the right size, but also the right shape. Table 4: Straightness and Flatness (Class h) Range (mm) 100 to 300 300 to 1000 1000 to 3000 Class h (High) Table 5: Perpendicularity (Class h) Range (mm) 100 to 300 300 to 1000 1000 to 3000 Class h (High) Table 6: Symmetry and Circular Run-out Symmetry (Class h): 0.5 mm maximum. Circular Run-out (Class h): 0.1 mm maximum. Why Use ISO 2768-mh?

Cleaner Drawings: You don't have to clutter your CAD exports with "±" values for every single fillet or shoulder.

Cost Efficiency: Using "Medium" tolerances for non-critical areas prevents the machine shop from over-engineering the part, which saves you money. The Core Data: ISO 2768-mh Tolerance Chart (Linear

Global Standardization: Whether your part is being machined in Germany, the US, or China, "ISO 2768-mh" means exactly the same thing. How to Indicate it on Your Drawing

To implement this, simply add a note in or near the title block of your technical drawing: General Tolerances: ISO 2768-mh When NOT to Use It

If a feature is critical for a "press-fit" (like a bearing housing) or requires extreme precision for airtight seals, do not rely on ISO 2768. In those specific cases, you must manually define a tighter tolerance (e.g., +/- 0.01mm) directly on that dimension.

The Core Data: ISO 2768-mh Tolerance Chart (Linear Dimensions)

The most critical part of this article is the actual chart. For general tolerances per ISO 2768-1, class Medium (m) , the tolerances are defined by nominal dimension ranges. Note that these are symmetrical tolerances (±) unless otherwise stated. The Ultimate Guide to ISO 2768-mh Tolerance Chart:

Summary of ISO 2768-mh

| Parameter | Value | |------------------------|----------------------| | Linear tolerance class | m (medium) | | Geometric tolerance class | H (precision) | | Typical application | General machining, turned/milled parts without individual tolerances | | Standard compliance | ISO 2768-1:1989, ISO 2768-2:1989 |

The Ultimate Guide to ISO 2768-mh Tolerance Chart: Precision for General Engineering

Real-World Example Drawing

Title block note: GENERAL TOLERANCES ISO 2768-mH

Dimensions on drawing:

• Outer length: 150 mm → ±0.5 mm allowed
• Hole diameter: 10.0 mm → 10.00 to 10.22 mm allowed
• Depth of blind hole: 12 mm → ±0.2 mm allowed
• Angle: 45° (no tolerance) → ±1° allowed
• Flatness of mounting surface: 0.2 mm max deviation over 100 mm

No need to add individual tolerances unless tighter control is needed.

Scenario 3: Thin Wall (0.8mm thickness)

• Issue: The chart starts at "0.5 up to 3mm" giving a ±0.1mm tolerance.
• Caution: A 0.8mm wall with a ±0.1mm tolerance means the wall could be 0.7mm. That is a 12.5% reduction. ISO 2768-mH is often too loose for thin-walled injection molded parts or delicate sheet metal.

2. External Radii and Chamfers (ISO 2768-1 – Class m)

| Nominal Size Range (mm) | Tolerance (mm) | |------------------------|----------------| | 0.5 up to 3 | ±0.2 | | >3 up to 6 | ±0.5 | | >6 up to 30 | ±1.0 | | >30 up to 120 | ±2.0 | | >120 up to 400 | ±4.0 |