The drawing is the law — what is not on it does not apply
In the ISO GPS world there is one clear principle: the drawing is definitive. Sounds unspectacular? Then you are seriously underestimating this principle — it is the backbone of every technical specification.
What does that mean?
Quite simply: all geometrical requirements on a part — for example form, orientation, location or surface texture tolerances — must be stated explicitly on the drawing, either:
- directly with GPS symbols (e.g. for flatness, for the maximum material requirement),
You can find all symbols in our ISO GPS symbol overview.
- by reference to sets of rules (e.g. "tolerancing per ISO 8015")
- or through general standards, such as national or company drawing standards.
What is not stated can neither be inspected nor claimed against. A later "but that's what we meant" simply does not count.
What applies to different part states?
A drawing can specify different states of the part — after machining, after coating, or in the final state. What matters is that each indication clearly shows which state it refers to. If it does not, the final state applies automatically.
Even if it is not on the drawing…
If any part of the ISO GPS system is used, for example a simple symbol such as the envelope requirement
then the entire ISO GPS world applies automatically — including all principles and rules of ISO 8015. Even if the drawing does not say so explicitly. Why a single symbol invokes the whole set of rules is explained in "I don't want ISO GPS! — But you have been using it all along".
Conclusion
The drawing is the only legally binding document for the part specification. If you want clear requirements, you have to state them visibly, unambiguously and in conformity with the standards.
