Dimensioning policy for assemblies: As a rule, assembly drawings are usually not fully dimensioned; only key overall, interface, and fit dimensions are shown, while individual part dimensions appear on detail drawings. Assess this statement.
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ACorrect: assemblies show limited critical dimensions, not full detail
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BIncorrect: assemblies carry every dimension of each part
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CIncorrect: assemblies never include any dimensions of any kind
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DIncorrect: dimensions must be placed only in parts lists
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EIncorrect: all dimensions are reserved for exploded views only
Answer
Correct Answer: Correct: assemblies show limited critical dimensions, not full detail
Explanation
Introduction / Context:Drawing packages typically include both assembly and detail drawings. Knowing which dimensions belong where improves clarity and avoids duplication or contradiction. Assemblies emphasize relationships and fits; details carry complete manufacturing information for each part.
Given Data / Assumptions:
- We are discussing production documentation, not conceptual schematics.
- Detail drawings exist for manufactured components.
- Assemblies must communicate how parts relate and interface.
Concept / Approach:Assembly drawings focus on mating conditions, reference datums, installation envelopes, overall size, and critical interfaces (bolt circles, clearances, shaft-to-bore fits). Detail drawings (or model-based definition) provide all feature sizes, tolerances, and finishes for individual parts. This division of information prevents conflicting numbers and keeps the assembly sheet readable.
Step-by-Step Solution:
Identify which dimensions affect fit and overall interfaces; place those on the assembly.Move feature-level dimensions (holes, slots, chamfers) to the relevant detail drawing.Ensure the bill of materials and callouts connect assembly items to their details.Verification / Alternative check:Compare a fully dimensioned assembly to a best-practice assembly. The best-practice version is cleaner, with only key dimensions, while the part details contain exhaustive size and tolerance data.
Why Other Options Are Wrong:
- Putting every part dimension on the assembly (option B) creates clutter and conflicts.
- Asserting “no dimensions at all” (option C) ignores necessary installation and fit dimensions.
- Parts lists (option D) are not a place for numeric geometry.
- Exploded views (option E) are pictorial aids, not the home for all dimensions.
Common Pitfalls:Duplicating dimensions across assembly and detail sheets; omitting critical interface tolerances; failing to note reference datums that drive assembly inspection.
Final Answer:Correct: assemblies show limited critical dimensions, not full detail