Does the tolerance really need to be that tight?
When putting a dimension on a drawing the designer should think of the manufacturing and measurement implications.
The question the designer should ask is ‘Does the tolerance need to be this tight for the part to function correctly?’
Consider if a diameter is toleranced at ± 0.001 mm this would mean that, as a rule-of-thumb, measurements need to be made with a measurement uncertainty at least ten times better, i.e., with a measurement uncertainty of 0.000 1 mm.
An uncertainty this low is only available from National Measurement Institutes such as NPL. To achieve this uncertainty will need specification of good surface texture and form (cylindricity in this case).
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Good practice online modules
- Dimensional
- Overview of basic design & interpretation of an engineering drawing
- An introduction to datum
- An introduction to geometric tolerancing
- An introduction to the designer's role in the design & interpretation of an engineering drawing
- An introduction to the manufacturer's role in the design & interpretation of an engineering drawing
- An introduction to the inspector's role in the design & interpretation of an engineering drawing