Part 1 of the standard focuses on the basic measurements of a part. It introduces four tolerance classes, ranging from very precise to very coarse: f (Fine)m (Medium)c (Coarse)v (Very Coarse)
Applies to rotating features. Class H allows 0.1 mm; Class K allows 0.2 mm; Class L allows 0.5 mm. How to Indicate ISO 2768 on a Drawing
In precision machining and CNC milling, the class is the most common industry standard. Linear Dimensions Reference Table iso 2768 general tolerances pdf exclusive
| Class | Designation | Description | Typical Application | | :--- | :--- | :--- | :--- | | | Fine | Highest precision among the classes. | Precision instruments, tight fits, high-cost components. | | m | Medium | The industry standard. Most drawings use this. | General CNC machining, turning, and milling. | | c | Coarse | Loose tolerances for non-critical features. | Castings, rough forgings, or parts where fit isn't crucial. | | v | Very Coarse | The loosest manufacturing tolerances. | Sheet metal fabrication and coarse structural components. |
If a single feature on a part requires a hyper-precise fit (like a bearing bore), manually override the general standard by writing a specific tolerance next to that exact dimension on the drawing. Part 1 of the standard focuses on the
While "exclusive" versions are the legal standard, unauthorized scans or PDF reproductions are common. Reliance on these documents poses technical risks:
While ISO 2768 is incredibly useful, relying on it blindly can introduce errors. Keep these modern manufacturing rules in mind: How to Indicate ISO 2768 on a Drawing
: Covers linear and angular dimensions (external sizes, internal sizes, radii, and chamfers). ISO 2768-2
The standard is divided into two critical parts:
For straightness tolerances, the relevant line length is considered. For flatness, the larger side length of the surface (or the diameter of a circular surface) is used.