Symmetry ensures that two features on a part are evenly spaced relative to a central datum plane or axis. Under class K, symmetry is tied to the longest feature: Nominal Length Range (mm) Symmetry Tolerance (mm) over 100 to 300 over 300 to 1000 over 1000 to 3000 Run-Out (Circular Run-out)
Before focusing on the "mk" classification, it is essential to understand the parent standard. ISO 2768 is an international standard titled "General tolerances for linear and angular dimensions without individual tolerance indications."
A design engineer creates a mounting bracket for an electric motor. The bracket has: general tolerance iso 2768-mk
Part 2 focuses on the "form" of the part. There are three classes: H, K, and L. The class is the medium-level requirement for geometry.
Defines geometric tolerances (form and position). The 'K' stands for "K" class (a moderate level of precision). Symmetry ensures that two features on a part
Understanding General Tolerance ISO 2768-mk In the world of precision manufacturing, specifying a tolerance for every single dimension on a technical drawing is both time-consuming and prone to error. is an international standard designed to solve this by providing "general tolerances" that act as a default for any dimension without an individual specification.
This is where ISO 2768-mk becomes stricter than the 'f' (fine) class. Class 'k' tolerances are tighter than 'L' (coarse) but looser than 'H' (precision). The values depend on the of the feature. The bracket has: Part 2 focuses on the "form" of the part
Perpendicularity defines the allowable deviation from a perfect 90-degree angle between two surfaces. It is based on the longer of the two sides forming the angle. Nominal Length of Shorter Line (mm) Perpendicularity Tolerance Class K (mm) 100 to 300 300 to 1000 1000 to 3000 3. Symmetry
Reduces drawing complexity by eliminating the need to label every single dimension with a specific tolerance.
Functionality. 'cL' is too loose for sliding fits, rotating shafts, or aligned mounting holes. 'mk' ensures basic interchangeability.
Circular run-out tolerances under Class K are limited to a maximum variation of across the surface, regardless of the part's size. Why Use ISO 2768-mK?