(Note: ′ = minutes of arc. 60′ = 1 degree.)
This is where saves the day. Specifically, its rules for angular tolerances.
Disclaimer: Always refer to the latest official ISO 2768-2 standard for exact tables and regulatory requirements before production. iso 2768 angular tolerance
For general tolerancing, ISO 2768-1 (for linear dimensions) gets all the attention. But its lesser-discussed sibling, , handles features like angles, chamfers, and tapers. Ignoring it is a fast track to rejected parts or inflated machining costs.
| Class | Code | Typical Application | | :--- | :--- | :--- | | | f | Precision instruments, tight assemblies | | Medium | m | General machining (most common default) | | Coarse | c | Fabrication, welded structures | | Very Coarse | v | Sheet metal, rough castings | The Catch: It Depends on Leg Length Here is the most misunderstood aspect of ISO 2768 angular tolerances: The tolerance is not a fixed angle (e.g., ±1°). (Note: ′ = minutes of arc
The standard provides a table of . The Short Version (Angular Tolerance Table) For Shorter leg length up to the specified range, here are the rough equivalents (always consult the official standard for production):
You have a 45° chamfer on a 15mm long edge, with "ISO 2768-m" (Medium). Look at the row for 10–50mm. The tolerance is ± 40′ (40 minutes) . That is roughly ±0.66°. A Common Design Mistake Mistake: Drawing a 90° corner on a 200mm bracket and writing "ISO 2768-f" (Fine). Reality: Fine class for a 200mm leg gives you roughly ±5′ (0.08°). That is incredibly tight. The machinist will need to set up the part on a sine plate or use a CMM to verify. Your "simple" bracket just became expensive. Disclaimer: Always refer to the latest official ISO
If you have ever sent a 2D drawing to a machine shop and received a call asking, “How tight do you actually need this chamfer to be?” — you have experienced the gap between "design intent" and "manufacturing reality."