Angular tolerances depend on the length of the shorter leg of the angle being measured. Length of Shorter Leg (mm) Tolerance Limits for Class m 120 to 400 ISO 2768 Part 2: Geometrical Tolerances (Class K)
The standard represents the "Medium" standard of modern manufacturing. It balances manufacturing cost with functional reliability. By applying this standard, companies reduce drawing clutter, minimize misinterpretation, and ensure that parts are manufactured to a consistent, acceptable quality level.
The designation combines two different parts of the standard:
1. Part 1: Linear and Angular Dimensions (The lowercase "m") general tolerance iso 2768-mk
: Refers to ISO 2768-2 . This part covers geometrical tolerances (GD&T) for features like flatness, straightness, parallelism, and perpendicularity.
Because it is an international ISO standard, a drawing created in Germany using ISO 2768-mK can be accurately interpreted and manufactured by a machine shop in Japan or the United States without communication barriers. Limitations: When Not to Rely on ISO 2768-mK
Symmetry tolerances apply to features that share a common central axis or plane. The value is based on the longest of the relevant features. Nominal Length Range (mm) Symmetry Tolerance Class K (mm) 100 to 300 300 to 1000 1000 to 3000 4. Run-Out (Circular and Total) Angular tolerances depend on the length of the
O-ring grooves and sealing surfaces require incredibly tight control over depth and surface finish to prevent leaks.
If a feature is purely aesthetic or clears a wide open space, applying an "m" tolerance might make the part more expensive to manufacture than necessary. You can specify a coarser class or a broad block tolerance for those areas.
: Represents the Medium tolerance class for linear and angular dimensions (lengths, radii, angles). By applying this standard, companies reduce drawing clutter,
For basic dimensions like lengths, widths, heights, and diameters, class "m" dictates the following symmetric tolerances: Nominal Dimension Range (mm) Permissible Deviation (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
It immediately signals to the manufacturer which dimensions are critical (those with custom tolerances explicitly written out) and which are standard fit features. How to Apply It on a Drawing
The Definitive Guide to General Tolerance ISO 2768-mK In manufacturing, achieving absolute perfection is impossible. Every machined component varies slightly from its theoretical design dimensions. To control these variations without cluttering engineering drawings with individual tolerances, manufacturers rely on international standards.
It ensures that a machine shop in one country interprets "no tolerance" the same way as a shop in another. Part 1: Dimensional Tolerances (The "m")
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