General Tolerance : ISO 2768

General tolerance ISO 2768 does not specify where to use these tolerance. As per design requirement and manufacturing capability tolerance class is defined. For example : For sheet metal parts ISO 2768mk is used. And for machined components ISO 2768fh can be used. In above example “m” and “k” has defined the tolerance class. 

Critical dimensions tolerance is calculated using tolerance stackup analysisYou can also use tolerance stack up calculator for this purpose.

It is not possible to define tolerance against each dimension. Therefore variation in dimension without tolerance are defined using general tolerance. ISO 2768 has defined general tolerance for:

  • Linear Dimensions
  • Angular Dimension
  • External Radius and Chamfer height
  • Geometric Tolerance such as straightness, flatness, perpendicularity, symmetry and runout.

General Tolerance : ISO 2768

Linear Dimensions
Nominal Length Range in mm Tolerance Class
f (fine) m (Medium) c (coarse) v (very coarse)
0.5 up to 3 ±0.05 ±0.1 ±0.2
3 up to 6 ±0.05 ±0.1 ±0.3 ±0.5
3 up to 30 ±0.1 ±0.2 ±0.5 ±1
30 up to 120 ±0.15 ±0.3 ±0.8 ±1.5
120 up to 400 ±0.2 ±0.5 ±1.2 ±2.5
400 up to 1000 ±0.3 ±0.8 ±2.0 ±4.0
1000 up to 2000 ±0.5 ±1.2 ±3.0 ±6.0
2000 up to 4000 ±2.0 ±4.0 ±8.0
External Radius and Chamfer Heights
Nominal Length Range in mm Tolerance Class
f (fine) m (Medium) c (coarse) v (very coarse)
0.5 up to 3 ±0.2 ±0.2 ±0.4 ±0.4
over 3 up to 6 ±0.5 ±0.5 ±1.0 ±1.0
over 6 ±1.0 ±1.0 ±2.0 ±2.0
Angular Dimensions
Nominal Length Range in mm Tolerance Class
f (fine) m (Medium) c (coarse) v (very coarse)
up to 10 ±1° ±1° ±1°30′ ±3°
over 10 up to 50 ±0°30′ ±0°30′ ±1° ±2°
over 50 up to 120 ±0°20′ ±0°20′ ±0°30′ ±1°
over 120 up to 400 ±0°10′ ±0°10′ ±0°15′ ±0°30′
over 400 ±0°50′ ±0°50′ ±0°10′ ±0°20′
Straightness and Flatness
Nominal Length Range in mm Tolerance Class
H K L
up to 10 0.02 0.05 0.1
over 10 up to 30 0.05 0.1 0.2
over 30 up to 100 0.1 0.2 0.4
over 100 up to 300 0.2 0.4 0.8
over 300 up to 1000 0.3 0.6 1.2
over 1000 up to 3000 0.4 0.8 1.6
Perpendicularity
Nominal Length Range in mm Tolerance Class
H K L
up to 100 0.2 0.4 0.6
over 100 up to 300 0.3 0.6 1
over 300 up to 1000 0.4 0.8 1.5
over 1000 up to 3000 0.5 0.8 2
Symmetry
Nominal Length Range in mm Tolerance Class
H K L
up to 100 0.5 0.6 0.6
over 100 up to 300 0.5 0.6 1
over 300 up to 1000 0.5 0.8 1.5
over 1000 up to 3000 0.5 1 2
Runout
H K L
0.1 0.2 0.5

Conclusion

To sum up, Engineering tolerance is very important and critical part of product design. And ISO-2768 standard defines the values of general tolerance. It is always recommended to run tolerance stackup analysis before design finalization. 

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You can Check in detail about Limit Fit and Tolerance Here. 

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