2768-mk [2021] | General Tolerance Iso

ISO 2768-2 covers geometrical features using three classes: H, K, and L. Class "K" is the medium standard for form and position tolerances. 1. Straightness and Flatness

: For applications requiring high precision, such as certain aerospace or medical device components, tighter and more specific tolerances may be necessary.

Below is a snapshot of the allowable deviations for linear dimensions under the "m" (medium) class: Dimension Range (mm) Tolerance (± mm) 120 to 400 400 to 1000 Best Practices for Implementation

Perpendicularity requires a datum feature. The tolerance depends on the length of the shorter leg forming the 90∘90 raised to the composed with power Nominal Length Range ( Tolerance Limit for Class "K" ( 3. Symmetry general tolerance iso 2768-mk

| Nominal Length Range of Shorter Side (mm) | Permissible Deviation (mm) | | :--- | :--- | | up to 100 | 0.4 | | over 100 up to 300 | 0.6 | | over 300 up to 1000 | 0.8 | | over 1000 up to 3000 | 0.8 |

is the go-to default for general machined parts in most workshops. It balances cost, inspectability, and functionality. Always verify that your feature tolerances (especially form) are adequate for assembly – if not, add explicit GD&T.

While powerful, ISO 2768 is not a blanket solution for every feature. It should not be applied to: ISO 2768-2 covers geometrical features using three classes:

For class "k", the general circular run-out error must not exceed .

Instead of placing ±0.2 or ±0.5 on fifty different dimensions across a drawing, a single note in the title block covers them all.

The 'k' class generally allows a symmetry deviation of 0.6mm. Run-out: Circular run-out for class 'k' is typically 0.2mm. Why use ISO 2768-mk? Straightness and Flatness : For applications requiring high

: The general tolerance for circular run-out under class K is . 5. Benefits of Implementing ISO 2768-mk

ISO 2768-1 features four tolerance classes: fine (f), medium (m), coarse (c), and very coarse (v). The "m" class balances manufacturing feasibility with functional precision.

However, it is not a magic wand. Always ask yourself: “If this dimension drifts by 0.2mm, will my assembly fail?” If the answer is yes, add a specific tolerance (e.g., 10.0 ±0.01mm ) directly next to that dimension.

What are you using (e.g., CNC milling, 3D printing, sheet metal)? Are you dealing with any critical mating parts ? Share public link

) directly next to that specific dimension on the drawing. Specific callouts always override general standards. Best Practices for Designers and Machinists