Are these acceptable? The answer depends on the specified tolerance standard. If the drawing uses , the general tolerance for a dimension between 30 mm and 120 mm is ±0.3 mm (as per Table 1). Therefore, the acceptable range for the diameter is 49.7 mm to 50.3 mm . In this case, the parts with diameters of 47.8 mm and 52.5 mm would be out of tolerance and should be rejected.
| Nominal Size Range (mm) | Tolerance ‘m’ (± mm) | | :--- | :--- | | 0.5 to 3 | 0.1 | | >3 to 6 | 0.1 | | >6 to 30 | 0.2 | | >30 to 120 | 0.3 | | >120 to 400 | 0.5 | | >400 to 1000 | 0.8 | | >1000 to 2000 | 1.2 |
Perpendicularity limits are based on the length of the shorter leg forming the right angle: Nominal Length Range (mm) Perpendicularity Tolerance Class "K" (mm) 100 to 300 300 to 1000 1000 to 3000 Symmetry and Run-out
Used for precision engineering and tight-fitting components. general tolerance iso 2768-mk
The allowable deviations depend on the nominal size of the dimension. Below is the table for Class "m":
: Refers to ISO 2768-2 , which defines geometric tolerances such as flatness, straightness, and perpendicularity. When to Use This Callout
The Three Tolerance Classes for Geometrical Tolerances (Part 2) Are these acceptable
In manufacturing, perfection is impossible. Every part coming off a CNC mill, lathe, or sheet metal bender will have tiny variations in size and shape. If engineers had to specify an individual tolerance for every single dimension on a complex blueprint, drawings would become unreadable, and design time would skyrocket. This is where comes in.
If a specific feature requires tighter tolerances than what class provides (e.g., a precise bearing press-fit), the designer must manually write that specific tolerance directly next to the dimension line. The custom dimension will override the general ISO standard. 7. Industry Alternatives
Bearings usually require precision fits down to the micrometer level (e.g., +0.005mm / -0.000mm). The general ±0.1mm or ±0.2mm tolerance of class "m" will result in components that are either too loose or impossible to assemble. Therefore, the acceptable range for the diameter is 49
Note: Dimensions below 0.5 mm are typically handled by specific indications, as general tolerances may vary.
The uppercase represents the tolerance class for geometrical characteristics (Part 2). Deconstructing ISO 2768-mK
Covers external radii and chamfer heights for deburred or rounded edges. 2. ISO 2768-2: Geometrical Tolerances (Class 'K')