A short decimal display can conceal finer stored geometry. It does not create a new tolerance around that display.
Identify the representation precision
A model dimension's displayed value can be rounded to fewer decimal places than its underlying value. Changing the display precision changes the numeric presentation; it does not necessarily change the stored geometric quantity. Primary reference: Autodesk: rounded display values and precise model dimensions.
A permitted dimensional interval must come from its actual specification. Do not infer an allowable plus-or-minus range solely from the number of visible decimal places unless the released drawing expressly defines such a rule. Display and requirement are different records.
Compare invented rounded values
Imagine nominal model lengths 10.041 mm and 10.049 mm, both shown to one decimal place under conventional nearest rounding. Each displays 10.0 mm despite their different stored values. Their difference is 0.008 mm and remains absent from that short display.
This illustration supplies no actual manufacturing tolerance or acceptable difference. Another rounding convention or display setting would need its own interpretation. Matching short strings therefore does not prove identical nominal geometry, and adding more displayed digits alone does not establish a new design requirement.
Retain the quantity required by the handoff
Identify the released nominal value, the source model definition and the separately stated limits. When a comparison depends on more detail than the annotation shows, obtain the applicable precise value rather than estimating it from the rounded text.
If precision is changed for readability, review whether the presentation still communicates the intended interface. Preserve any actual tolerance notes and the responsible interpretation of the drawing. The conclusion should state whether geometry, presentation or the requirement changed; those three changes can have different consequences for a receiver preparing a mating part.
Customer Questions
Does more display precision necessarily change the model?
No. It can change only the presentation.
Do the fictional matching displays prove equal values?
No. The stated model lengths differ by 0.008 mm.
Where should allowable limits come from?
Use the actual released specification and its defined interpretation.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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