Standards vocabulary: what do we call the theoretically exact size from which the limits of size (upper and lower permissible values) are established for a feature?
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AActual Size
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BDimensioned size
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CProduction size
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DBasic size
Answer
Correct Answer: Basic size
Explanation
Introduction / Context:Limits and fits systems are built around a reference size. This reference is not a measured value but a theoretically exact starting point used to derive permissible variation.
Given Data / Assumptions:
- A feature has an upper and lower limit of size.
- Those limits are derived from a common reference value.
- We need the standard term for that reference.
Concept / Approach:“Basic size” is the theoretically exact value from which tolerances are applied to produce limits. It underlies hole-basis or shaft-basis fits and is fundamental to tolerance charting.
Step-by-Step Solution:
Identify that the size in question is a theoretical reference, not measured.Recall definitions: basic size vs. actual size vs. nominal/dimensioned size.Select “Basic size” as the correct term.Verification / Alternative check:Review standards tables (e.g., ISO fits): basic size is the column heading from which tolerances are applied to obtain limits.
Why Other Options Are Wrong:
- Actual Size: measured value on the produced part.
- Dimensioned size: the printed nominal; may equal the basic but not necessarily emphasized as theoretical reference.
- Production size: not a standard term.
Common Pitfalls:Assuming “dimensioned size” and “basic size” are always identical; in GD&T contexts, “basic” may appear boxed to denote theoretically exact dimensions (for locations or profiles), which is distinct from limits-of-size basics.
Final Answer:Basic size