1.4 Fundamental rules (o)

[Andrew T]

(o) Dimensions & tolerances apply only at the drawing level where they are specified. A dimension specified for a given feature on one level of drawing (e.g., a detail drawing) is not mandatory for that feature at any other level (e.g., an assembly drawing).

Does this read that a dimension & its tolerance, used on a part drawing, is maintained for that part, onto the assembly drawing, even though said dimension and tolerance are not repeated on the assembly drawing? Or, does this read that if a dimension & its tolerance are not repeated on the assembly drawing that the dimension & tolerance cannot be enforced in the assembly?

To me it reads the first way. Assuming that I am reading it correctly I pose the question below.

If I have a diameter dimension, shown only on a part drawing, that I need maintained in the assembly state, after a crimping operation has been performed, do I need to call out the diameter dimension again on the assembly print? As a general rule my company does not like this approach as a person writing an engineering change request could easily forget that the dimension exists on two prints. A note stating that the indicated diameter must not change size/shape from its component state is a better approach. However, does the wording in the standard eliminate the need for this note? Is this note already in effect due to the fundamental rules?

[Kelly_Bramble]

The rule means exactly what is reads...

Dimensions & tolerances apply only at the drawing level where they are specified.

If a hole feature is specified at the part level and meets dimensional conformance after manufacturing at the level... one cannot weld, bolt, machine or whatever modification at the next level of specification or manufacturing and expect the hole feature to conform to the lower level dimensional specification.

This is because the part can distort under bolt loading, reconfigure internal stress equilibrium due to the applied forces, removal of material or undergo distorsions due to welding or other processes.


If you have the identical hole dimension and tolerance specification on the next level engineering drawing - be prepared to modify or scrap should the feature not dimension or tolerance conform.